TECHNICAL

JOURNAL OF PROCEEDINGS

THE PERMANENT WAY INSTITUTION & THE UNION OF EUROPEAN RAILWAY ENGINEER ASSOCIATIONS

16TH OCTOBER 2018 - MANCHESTER CONFERENCE CENTRE UK

62 JOURNAL OF PROCEEDINGSTECHNICAL

Urban Railway: Infrastructure Engineering

As predicted, the UK has seen a large growth in rail Following our successful joint event in 2016 on the utilisation in both heavy and light rail in the last ten subject of High Speed Rail, I am delighted to welcome years. Tram systems have developed and expanded, our colleagues from all over the UK and Europe again there have been new innovations and the extensive to Manchester for this joint seminar on Urban Rail. urban system has been enhanced with more There are representatives from rail infrastructure trains and routes. This has given the rail and track providers, suppliers, consultants, contractors, infrastructure many challenges and this is why we government departments, universities and rail have focused this seminar on where engineers have specialists. been able to solve problems in the area of Urban Rail. We have papers on trams, train-trams and metro The Permanent Way Institution was formed in 1884 systems in Manchester, London, Milan, Sheffield to share track knowledge and has recently reacted and Vienna. We also look at some technical and cost sharply to enable it to rise to the modern challenge to based issues that inform our decisions. The papers provide essential technical support to the engineers in this journal have been selected through liaison involved in maintaining and improving the railways between the PWI and UEEIV. I would to thank Richard worldwide. The PWI is a member organisation and Spoors, Alison Stansfield and others for helping professional body that registers and qualifies rail to select the appropriate items for inclusion in the infrastructure engineers through the UK Engineering conference and supporting Journal of Proceedings. Council. A key role is the advancement of technical knowledge through meetings, conferences, seminars, Finally, I hope you enjoy the conference, discussing journals, textbooks and its comprehensive website the issues and reading the full transcripts of the www.thepwi.org. There are individual and corporate papers around this interesting and important subject members from every part of the UK rail industry and area. many international links. Brian Counter The partnership with UEEIV provides complete synergy in strategic objectives as they have a similar Technical Director role in mainland Europe. The UEEIV was founded in Permanent Way Institution 1990 and is the cooperation platform of 24 European [email protected] Institutes of railway engineers in 21 countries. The core function of the UEEIV is the registration of “EurRail-Ing”, the recognised European Railway Engineer title with over 300 registered engineers. The UEEIV is a strong and influential network of competent people in the railway sector and promotes contact between professionals working in the sector, the railways and the supply industry through seminars, conferences, symposia and exhibitions in Central Europe.

THE PERMANENT WAY INSTITUTION UNION EUROPEAN RAILWAY The Institution for Rail Infrastructure Engineers ENGINEERING ASSOCIATIONS www.thepwi.org www.ueeiv.eu

PLEASE NOTE The opinions expressed in this Journal of Proceedings are not necessarily those of the Editor or of the Institution or/and the UEEIV as a body.

63 JOURNALTECHNICAL OF PROCEEDINGS

Databased renewal: AUTHORS:

Dipl.-Ing. Thomas Hammer Management in Dipl.-Ing. Thomas Hauser Dipl.-Ing. Werner Wehr urban rail networks Wiener Linien

INTRODUCTION WIENER LINIEN There are numerous reasons for this success, As such it is imperative for an urban rail one of which being the continuous expansion operator to have the ability to plan renewal MOBILITY IN VIENNA of the public transport network. works with operational requirements (short term) and strategic requirements (long term) Vienna is growing! According to current SUBWAY CONSTRUCTION in mind. forecasts, Austria’s capital city will reach a population of two million in the next five to ten The construction of the Viennese network Ensuring sufficient financial resources for the years. This population growth brings major began in 1969 and with the first sections of the maintenance and renewal of the track systems challenges to services of general interest U1, U2 and U4, a base network was created. demands precise knowledge of the current for the next decade, with the mobility sector The underground network in Vienna is already condition and the future development. The playing an important role. The mobility of the in its fourth expansion phase. With the “Urban objective is to provide a valid decision base Viennese is characterised by a high usage of Development Plan - STEP 2025”, the city of for the renewal work to be able to provide public transport. The Wiener Linien, the public Vienna has set itself the goal of achieving 80% an undisturbed service for the public with transport operator of Vienna, understand it of the modal split with environmentally friendly maximum cost efficiency. to be their task to fulfill the mobility needs of modes of transport (pedestrians, cyclists and the population in order to continue to make a public transportation). APPROACH valuable contribution to the high quality of life in the city of Vienna. In addition, the number of commuters in TRAM NETWORK - RENEWAL WORK the area of Vienna is expected to increase PUBLIC TRANSPORT in the future. As a result, Wiener Linien will TRACK - ACTUAL STATE reach the goal of 1 billion passengers a year In 2018, the Wiener Linien network includes 5 in the near future. In order to accommodate Wiener Linien started a project to answer this metro lines with a service length of almost 83 this development and to relieve the existing challenge called “gläserner Fahrweg” (literally km and 109 stations. The tram network is made system, the capacity of the network has to be glass track). The focus of this project was to up of 28 tram lines, it has an operating length increased. Extensive network analysis for new deliver a valid model for the Viennese Tram of about 172 km and more than 1,000 stops. subway-lines ensure a future-oriented and Track Network to enable the strategic and Wiener Linien operates the sixth largest tram sustainable network. The construction for the support the operative planning of renewal network in the world. 128 bus lines (including next subway expansion will start next year. works. commissions and nightlines) supplement the public transport service and serve more than CHALLENGE The so called “Infrastructure Database” of 4,200 stations with a total network length of Wiener Linien was used in this project as the around 850 km. For the fourth time in a row, Urban rail networks consist of tram and/ central data source and had to be expanded in Wiener Linien has achieved an increase in or metro systems. They are usually smaller the course of the project. passengers in 2017 and has reached a new than main lines and due to the environmental record of 961,7 million passengers. requirements in the heart of the city, they have As such, the whole track layout of the special specifications that often differ from the tram network has been represented as a The share of public transport of the modal split classic systems used on main lines. This is mathematical graph. The consecutive track in Vienna is 38%. In 2017, 778.000 people especially true for the available equipment on layout elements have been described as the held an annual travel card for Wiener Linien as the market, as well as the circumstances that element type itself (straight line, curve, etc) opposed to 300.000 in 2005. Thus, there are have to be taken into account when performing and the related parameters (length, radii, more annual passes in Vienna than registered renewal works. etc) and have been saved line by line in the cars.

Figure 1a: Track geometry Figure 1b: Track geometry

64 JOURNAL OF PROCEEDINGSTECHNICAL

Figure 2: Age of the tracks Figure 3: Life cycle matrix

Figure 4: necessary renewal work per year

Figure 5: Magic wear rate

Due to the implementation of information accumulated load and the track layout (radii) regarding the amount of traffic on a specific (see figure ).5 For additional verification section of the track using systems for timetable the theoretical remaining lifespan has been planning, the actual accumulated load could compared with the actual operational renewal be derived as an additional feature on each planning for the corresponding three years. section in the analysis process. Therefore the total load of the specific vehicle types (ULF A & - WORK IN PROGRESS AND FORECAST B, E1, E2 and C5) was used. The accumulated load is between 1 MGT/a and up to 10 MGT/a, The results of the model are very helpful in depending on the amount of operational lines, financial and operational planning. None the Figure 6: infrastructure database the vehicle mix and the respective intervals on less Wiener Linien is seeking an increase in - Example of curve radii of metro the specific track section. accuracy of the resulting model. network Combining this data on every track section, At the moment the following actions are being infrastructure database in human and machine as well as using regression analysis on carried out: readable form. This graph is used to locate the generated feature matrix, results in a relevant data and information of the network theoretical life span of track according to • Ongoing implementation of new data into itself. the features of accumulated load, radii and the model to increase the data basis track sections. Figure 3 shows the resulting • Calculation of the prediction model based As a first step the network has been analysed clustered life cycle matrix disregarding on newest track condition based on according to the track radii, which showed that statistical fluctuation. measured assessment about 2/3 of the network consists of straight lines (see figures 1a and 1b). Based on this model and the actual age of The following approaches are also being the track, the amount of necessary renewal considered: Due to a significant increased wear of the work was calculated as shown in figure 4. rail at stops due to braking and acceleration, The necessary average annual renewal work • Individualising the resulting life span/ these parts of the network have been specially was determined to be about 2.9% of total track wear rate based on the individual track marked. length which is equal to an average life span of section and cross check with the global tram track of about 35 years. approach. (A global approach can also In the next step, all information regarding always be used as a backup if local renewal works of the tram track has been To verify these results based on the measured measurements fail) digitalised and imported into the infrastructure life span of the track, a second approach • Include additional parameters like database. This step has been very important to has been used. For this the measured rail maintenance work (e.g. rail grinding, geo reference this information onto the specific wear of the tram rails, (using the data from welding, etc) track layout graph, so that now it is possible the tram track measurement car), has been to show the age of each part of the tram track used to assess the average degradations rate network (see figure ).2 of grooved tram rails taking into account the

65 JOURNALTECHNICAL OF PROCEEDINGS

Figure 7: Wear rate - Metro Wiener Figure 8: Infrastructure database - Figure 9: infrastructure database - Linien rail wear rail change prognosis

GROOVED RAIL SWITCHES alternatives for the passenger and the Due to the fact, that the simulation of the wear, operational significance of the track section for as well as the rail change model simulation is - ACTUAL STATE fault compensation. Furthermore, the impact of done for the service lines of the Wiener Linien slow driving distances was assessed. Metro Network within about 24 hours with a Switches are cost intensive and rather forecast time of 10 years, there is no restriction sensitive parts of the track. As such Wiener For track sections with the highest priority, the to do this calculation on a regular basis with the Linien decided to take a look at these track objective should be unrestricted operational newest available rail wear data. Additionally, elements specifically. management. In addition to safe operation, the rail change model allows the wear values to the aim is to reduce operating costs by be reset in the determined change section. As In contrast to track the radii of switches avoiding disruptions, to reduce the number a result simulations longer than the lifespan of don’t differ much, so the model has been of lost kilometers and to increase customer the specific rail section are possible. built ignoring the curve radius but including satisfaction. the accumulated load. Additionally the - WORK IN PROGRESS AND FORECAST environmental circumstances have been taken METRO NETWORK - RENEWAL WORK into account, so that switches are categorised Wiener Linien is interested in increasing into: - ACTUAL STATE the accuracy of the model with local model parameters instead of global line models and to • Switches in the depots In contrast to the tram network only changing create models for metro switches. • Switches connecting the depot and the the worn rail is possible. As such the focus service tracks of renewal work on the Wiener Linien Metro SUMMARY • Switches on service tracks network is mainly changing worn rails. The metro network has been described Wiener Linien does prediction modeling Again a feature matrix has been built and a similarly to the tram network in a geo regarding rail wear and remaining lifetime of resulting life span has been calculated. referenced graph including track section rails and track in the metro and tram network. In contrast to normal track, the actual condition specific track layout features see( figure ).6 These models are based on measured life class (clasess A to D) of switches is already spans of specific track layout and/or measured implemented in the infrastructure database Due to a large amount of available data wear. Having sufficient financial resources so the improvement, which is being worked regarding the wear of the rails, from the Metro for the maintenance and renewal of the track on regarding track is already used regarding measurement car of Wiener Linien it was systems demand precise knowledge of the switches. possible to derive a degradation model for condition and the future development. each Metro Line based on this data. As for The results are used in supporting the - WORK IN PROGRESS AND FORECAST the feature matrix, it could be reduced to only operational, as well as the strategic planning using the curve radii as an additional factor. process, to determine where and when specific Only the actual condition of switches is The result has been a simple formula, which renewal-work has to be carried out. categorised at the moment. Wiener Linien can be used to derive the amount of wear is thinking about new methods of assessing depending on the time and the actual radius of switch wear data, (especially in an automated the track section. The resulting graph is shown way), to increase the accuracy of the model in figure .7 and the resulting forecast of the residual life span of the individual switch. Based on this model, as well as the actual wear state of the individual rail, the point in time, - OPERATIONAL PRIORITISATION when the rail has to be changed, is calculated. On the downside, only using the wear The current budget situation does not allow as a trigger means it is not possible to the necessary renewal rates, which leads to a determine the length of rail which has to be maintenance backlog. changed. Therefore a rail change model was implemented using practical knowledge in the As a further basis for deciding at which usual procedure of changing rails in the metro location the maintenance budget should be network. To do this, the trigger point of the used, an operational prioritisation of the track worn rail has to be determined. From this point, infrastructure was undertaken. This included the model searches for a possible connection parameters such as the daily passenger point, where the worn rail and a new rail can be occupancy, existing transfer rates, connection connected (see figures 8 and ).9

66 JOURNAL OF PROCEEDINGSTECHNICAL

Permanent AUTHORS:

DI Thomas Hauser measuring systems Wiener Linien DI Hanno Töll for the assessment FCP of the long-term behaviour of massive wheels

ABSTRACT of massive wheels in terms of noise and rubber and a second steel ring expanding to a vibrations in comparison to resilient wheels is clearance fit pressed over the rubber element. The Viennese metro operator Wiener Linien low. A huge impact on the vibrations is based The wheel’s disc and ring are decoupled from currently uses conventional resilient wheels on the train and wheel set type. Furthermore, each other. The general assumption therefore on its metro trains. It is planned to replace the maintenance condition of the train is a is that rubber-sprung wheelsets have a better the current wheel type with massive wheels relevant criterion. As the project is still running, noise and vibration emission behaviour due to in order to potentially reduce maintenance the long-term behaviour is under evaluation. the elastic intermediate layer. costs. Nine measuring systems were installed Further findings are expected after the project within the metro network to analyse the long- conclusion in 2019. In order to assess this theory, Wiener Linien term behaviour of massive wheels and to decided to equip three trains of the type U2 demonstrate advantages and disadvantages INTRODUCTION with monobloc wheels for test runs. Since early compared to resilient wheels with regard to 2016 all three trains running within the metro noise and vibration impacts. By mid-2016 three The current standard wheel type of Wiener network have been permanently measured. train sets were equipped with massive wheels. Linien metro trains is a resilient wheel The measurements will be concluded by the Since then, the trains have been used for trial consisting of a bi-block with a rubber year 2019 after a period of 2 years. runs in the Viennese underground railway suspension in between two steel blocks. network. Monitoring stations within the network In 2016 Wiener Linien decided to start CONCEPT OF AUTOMATED are permanently recording data during train an assessment in order to investigate the PERMANENT MONITORING pass-bys. RFI -tags installed on the trains application of lower maintenance monobloc enable the identification of the train when wheels. The assessment focussed on the Single measurements represent only a passing each monitoring station. Selected effects of noise and vibration, long-term snapshot of the current state of the train’s indicators are permanently measured, post- behaviour and the interaction with the existing condition. Such measurements are not processed and transmitted in real time to a track systems. sufficient to assess the long-term behaviour of web-interface accessible by the client. the train. It is therefore essential to record and The difference between monobloc wheels observe each train passing by over a longer On the basis of approximately 2,000 daily and the conventional bi-block wheelsets is period of time. In order to achieve this, Wiener recorded trains, various statistical data is that monobloc wheels (figure )1 are made of Linien decided to install nine permanent gathered, providing information on train a single cast and thus represent a single disk. monitoring stations within the metro network on condition and on the impact of massive Bi-bloc wheels (figure )2 consist of a steel strategically selected locations. wheels. It has been shown that the impact element (wheel disk) coated with an element of Each of the measurement stations record up to 250 train pass-bys each day. It is therefore essential to provide automated measurement systems and post processing routines for

Figure 1: Monobloc wheel Figure 2: Bi-bloc wheel

67 JOURNALTECHNICAL OF PROCEEDINGS

Figure 3: Schematic overview of the measurement system in the tunnel Figure 5: Weather station

In order to associate the measured emissions to each train, a vehicle tracking and identification system was implemented. An active RFID-antenna has been installed in the track at every measurement section (figure 8). Each train of Wiener Linien was equipped with multiple units of passive RFID transponder tags (figure )9 in the front and the rear bogies of every train unit. The tags allow not only the identification of train type and train number, but also determine the running direction and average train speed. The installation also enables an accurate association of axle and measurement values.

MEASURING NOISE AND VIBRATION EMISSIONS

The measurement systems are in permanent operation but only record the data in the case of an event detected by a trigger. Recording time is dependent on the maximum train speed of the specific section; trains run at speeds of up to 80 kph. The sampling rate is defined with 1,200 Hz for standard applications. Sound Figure 4: Measurement section on elevated viaduct structure measurements are recorded with a higher frequency of up to 50,000 Hz. The collected raw data is saved locally on a hard drive at effective monitoring. The measuring systems In addition to the above mentioned sensors, each station. Specific values such as train record each pass-by based on triggered the measurement stations located outside the number, maximum peak values of ground measurements including an adequate period of tunnels (figure )4 are equipped with sound borne noise and vibrations, train speed and before and after the train passing. level meters for sound recording as well as a weather data run through an automated post- weather station (figure )5 in order to record processing routine and are uploaded to a data Figure 3 displays the two main types of temperature, amount and type of precipitation, server by mobile network in real-time. This measurement systems installed in tunnels as wind and air pressure etc. data can be accessed directly via a custom well as outdoors. Based on their location, the fitted web-interface. Real-time transmission systems differ slightly in the sensor equipment. Measurement systems located in tunnels of this information allows detection of trains All systems consist of acceleration and (figure )6 include acceleration transducers with high emissions. In the event of trains with vibration transducers mounted on the rail, on mounted on the tunnel walls (figure 7) to considerably higher emissions, a notification the sleeper, the track slab or, in the case of assess vibration transfer and propagation can be shared to the competent department for elevated sections, directly on the supporting characteristics of the structure. train maintenance of Wiener Linien. structure. The rail foot is equipped with two strain gauges on each rail in order to determine stresses and the velocity of the running trains.

68 JOURNAL OF PROCEEDINGSTECHNICAL

Figure 6: Tunnel measurement system Figure 7: Accelerometer on tunnel wall

Figure 8: RFID antenna installed in the track (right) Figure 9: RFID transponders installed on the train

FINDINGS IN REGARD TO FINDINGS IN REGARD TO with conventional bi-bloc wheels (Type 2b), but VIBRATIONS AIRBORNE NOISE still significantly lower emissions than the basic population set of all trains. The four different train types running in the Due to limited space, the sound level meters Viennese metro network (Train types 1 to 4) are located at different positions on each LONG TERM BEHAVIOUR AND behave very differently in regard to vibrations. measurement section. In order to allow a MAINTENANCE CONDITION Figure 10 shows the maximum resulting comparison of the noise emissions recorded vibration velocities vR,max on one measurement at various sections, the measured emissions Train types 1 and 2 are permanently modified section over a period of 3 months. The graph were converted to a fixed point at a distance in their composition depending on the service shows the records of the sensor located on the of 7.5 m from the track axis and a height of 1.5 requirements, but it is possible to determine slab track (GTP). Train type 4 was not running m above the rail level, in accordance with the the train’s long-term behaviour only in the on this specific section and is therefore not relevant standards. case of a constant composition of one single shown in the graphs. unit. Only train type 3 consisting of one single Table 1 shows the average equivalent sound unit can be used to draw conclusions about It can be shown that train type 3 causes level of a 3-month evaluation period LA, eq on maintenance concepts. Since the trains are the highest vibration emissions in general. two measurement sections with different track permanently running on each line of Vienna’s Furthermore, this train type is characterised by systems and different train types. metro network, the trains are also recorded on a very high variance in measured values. On different measuring sections. Due to differing one hand this can be explained because of the The values in table 1 show a similar track systems (standard track, ballasted and largest sample size, but on the other hand also conclusion as for vibrations. Train type 3 is ballastless sections, mass-spring systems), due to a more inhomogeneous composition of generating the highest noise emissions of all the emission behaviour is expected to change the train fleet of train type 3 compared to trains trains. Trains with monobloc wheels (Type 2a) as well from section to section based on of the types 1 and 2. cause slightly higher emissions in comparison characteristic insertion loss. to the reference category of the same trains The three trains equipped with monobloc wheels (Type 2a) showed very little variance at the beginning of the measurements, explainable due to the new wheel condition. Over the course of the investigation, one of the three trains showed a significant deterioration regarding vibration emissions. This specific train generated vibration velocity values between 50 and 100 mm/s clearly visible in Figure 4 spreading apart from the other two trains of the reference category with monobloc wheels. Such knowledge indicates the requirement for maintenance. Table 1: Overview of train types, axle loads and equivalent sound level

69 JOURNALTECHNICAL OF PROCEEDINGS

It is essential to take this aspect into account for the evaluation of the long-term behaviour. The evaluation is therefore based on section specific trend curves. The slope represents the increase in emissions over time.

Figure 11 shows such trends for a selected type 3 train. It can be clearly seen that the emissions increase in trend over the evaluated 12 months period. The slope is depent on the track system of the measurement section. At the end of July 2017, maintenance works were undertaken (re-shaping of the wheels), resulting in a considerable reduction of emissions by more than 50%. In addition, it could be determined that the slope of the trend curve after completion of the maintenance works is significantly lower than in the previous period. It therefore can be concluded that the deterioration over time does not increase linearly, but rather exponentially. Based on this finding it can be stated that a protraction of maintenance works of the train has a significant negative impact on vibration emissions.

CONCLUSION

The evaluation of approximately 2,000 train pass-bys per day provides information on the possible application of monobloc wheels in the Vienna Metro system. The results of the evaluation indicate that trains with monobloc wheels generate higher noise and vibration emissions than the reference category of the same type of trains with conventional bi- block wheels with a rubber suspension. This statement has to be seen in relative terms however, as trains with monobloc wheels still cause significantly lower emissions than the basic population set of all trains.

In addition to the statements on the use of trains with monobloc wheels, further findings on the long-term behaviour and maintenance status of the trains have emerged. It has been proven that maintenance works on the train are able to reduce vibration emissions by more Figure 10:Maximum resulting vibration velocity vR,max for different trains than 50%. The slope of the deterioration trend curve after completion of the maintenance recorded on the slab track works is significantly lower than in the previous period. It can therefore be concluded that the deterioration over time does not increase linearly, but rather exponentially. Based on this finding it can be stated that protraction of maintenance works on the train has a significant negative impact on vibration emissions.

Permanent measuring systems on the network of Wiener Linien will continue to be under operation until 2019, investigating permanently the impact of monobloc wheels. Further findings are expected to be published after completion of the project in 2019.

Figure 11: Long term behaviour and increase of vibration emission. Maintenance works completed on 25.07.2017

70 JOURNAL OF PROCEEDINGSTECHNICAL

Elastic elements AUTHORS:

Peter Veit in track influencing Graz University of Technology, Austria

Stefan Vonbun total track costs Getzner Werkstoffe GmbH, Austria and reducing vibrations

INTRODUCTION On the one hand the results show the The tests and the analyses of the change effectiveness of track stabilising; on the other of track behaviour led to the general Under Sleeper Pads (USP) are associated with hand, high ballast degradation when using implementation of under sleeper pads having a positive impact on track behaviour of concrete sleepers is evident. The hard-to-hard for concrete sleepers at Austrian Federal ballasted track and reducing vibration. situation in this contact area causes only a few, Railways. The respective regulations are highly overloaded contact points forming the in power since 2007. Figure 2 depicts the IMPACT OF UNDER starting points for a limited number of “force- implementation of Under Sleeper Pads on the paths” through the ballast structure rather than network of the Austrian Federal Railways over SLEEPER PADS ON TRACK allowing the entire ballast structure to act as a time. There are still some wooden sleepers SUSTAINABILITY sleeper-support. Edges and corners are quickly installed e.g. on sharp curves, sidings and cracked off, leading to these unpredictable branch lines. Concrete sleepers without USP Starting with the impact on track behaviour initial settlements. As the number of “force- are built in mainly in case of single sleeper one question should be addressed: Why do paths” varies under neighbouring sleepers, the exchange and short sections of track renewal. concrete sleepers need further development? sleepers settle differently, causing initial errors; The reason is to avoid too many places where The implementation of concrete sleepers has equal to a reduced initial quality and increasing superstructure with and without USP meet, given track much better stability in increasing the rate of deterioration. To summarise: the as these two types of superstructure show the lateral track resistance and thus lowering bigger the contact area, the smaller the initial significantly different behaviour. the maintenance requirements. The one world settlement is and thus the differences between record run in 1955 with 331 km/h destroyed these settlements; the higher the contact area Track behaviour is evaluated when analysing the wooden sleeper track. There were two between sleeper and ballast the higher the time sequences of track recording data. In the main reasons: little lateral track resistance initial track quality. case of USPs, up to 2017, 60,000 sections due to the light superstructure and the manual with USP have been compared with respective maintenance not allowing continuity of track These results have been very promising from sections without USP. It can be shown that quality, neither in track laying nor within track a technical point of view. However, installation track deterioration is cut in half with regards maintenance. of Under Sleeper Pads can cause additional to levelling-lining-tamping. This is caused by investment costs. To analyse the efficiency of an increase of the contact area between the These problems were solved impressively long this additional investment from an economic sleeper and the ballast bed. Measuring in track before Under Sleeper Pads were in use by point of view, the technical effects (track quality and lab shows up to three times higher contact implementing mechanised track renewal and behaviour) must be analysed over the entire areas using USP. This reduces the stresses maintenance and heavy superstructure with 60 service life of track (life cycle costing) as just a in the ballast bed. Furthermore, it also has a kg rails and concrete sleepers. After the world life cycle approach allows the evaluation of the very positive impact on track service life as record run in 2007 at 574.8 km/h, the track was economic efficiency of various track types. In in case of good subsoil worn out ballast is opened for operation without any maintenance order to do this the behaviour of track must be limiting track service life. In Austria, there are action necessary. Furthermore, concrete analysed, as understanding of track behaviour also hundreds of switches equipped with USP. sleepers are cheaper than wooden ones and is the precondition of forecasting it and thus Based on the analyses of track behaviour a life show a longer service life. Thus, not only loads evaluating life cycle behaviour and life cycle cycle cost evaluation was conducted taking and speeds could be increased but also the cost of track. Within an extensive research the above described effects on track behaviour life cycle cost of superstructure was reduced program at Graz University of Technology in into account. by using concrete sleepers. However, concrete cooperation with the Austrian Federal Railways sleepers still show one main disadvantage Infrastructure, track behaviour over time was TRACK QUALITY BEHAVIOUR compared to wooden ones: the contact area analysed. between the sleeper and ballast is very small. When describing track quality behaviour, Tests using black paper below the sleepers All the following results described are various conditions such as transport volume, allowed the contact area between ballast and based on the extensive data of the Austrian type of superstructure, quality and status of all sleeper after tamping to be identified. The Federal Railways. Testing Under Sleeper components, alignment (radii), ballast quality, used ballast in Austria has a maximum size of Pads had already started in the late 1990s. quality of sub-layer as well as sub-soil, the 63 mm. The use of a dynamic track stabiliser Implementation of USP in ballasted track in functioning of the dewatering system, position (DGS) showed significant differences in the Austria began roughly 20 years ago. of stations, bridges and turnouts must be taken results as presented in figure .1

71 JOURNALTECHNICAL OF PROCEEDINGS

into account. Therefore, a data-warehouse was This underlines the expectations of Under lives. The LCC analysis plainly demonstrates set up covering track recording car data (initial Sleeper Pads as stresses in the ballast bed the total cost which may aid in management status, present status, and quality figures), type are reduced due to the increasing contact area discussions. and age of superstructure and sub-structure between sleeper and ballast (figure 3a). and transport load. The research was based However, there are other decision factors that on this data for the main railway network LIFE CYCLE COSTING need to be addressed: risk, future availability, of Austrian Federal Railways covering time best maintenance practices and environmental sequences over the past 17 years (figure ).3 Life Cycle Costing (LCC) is a process whereby concerns, just to mention a few that may be costs of various project alternatives are unique to a certain project. Some of these This structure allows the comparison of considered for building and maintaining an factors may be addressed by increasing future different types of superstructure for a big asset. These alternatives must all provide costs. As LCC addresses only those decision number of sections facing the same boundary the same level of service and benefits to be factors that can be stated monetarily, costs of conditions. The comparisons can be done effectively compared using LCC. Total costs operational hindrances become important in every 5m for a data set of 4,000 km in total under the LCC methodology are initial design describing costs of reduced availability. and thus provides a big number of comparable respectively the costs of re-investment and Application of LCC techniques provides sections. This allows the identification of the construction, ongoing maintenance costs and management with an improved awareness effects of initial quality as well as calculating scrap value or disposal cost for the previous of the factors that drive cost. Thorough the specific deterioration rate for a given set asset. All these costs are gathered for each analysis of the construction and the ongoing of boundary conditions and different types of alternative. Then the user discounts the costs maintenance are outlined in detail so as to superstructure. back to present day Euros and summarises make omissions more obvious to the LCC them. Engineering departments typically have creators. It is important that the cost drivers are The results are very promising as the ballast problems with convincing management to identified as completely as possible so that the is identified to be the element limiting the accept a higher initial cost in order to save ultimate decision makers can make the most economic service life of track. on maintenance or to allow longer service informed decision.

Two attributes of permanent way make life cycle costing especially useful in the field of railway infrastructure: an extremely long service life and a strong relation between initial quality, maintenance demands and service life. Investment determines the initial track quality, while maintenance affects future track quality and service life. Both investment and maintenance strategies must be considered together, as focusing on investment strategies or isolated maintenance regimes will lead to sub-optimal decisions.

It is difficult to predict the total life cycle cost of long-lasting assets because of the likelihood that there will be unexpected changes related to component costs and maintenance productivity. Moreover, LCC analyses usually focus on the factors and cost categories that are most affected by the alternatives that are being investigated. Therefore, the LCC values Figure 1: Contact area sleeper – ballast that result from a study are not necessarily complete or accurate or suitable for decision- making.

It is much better to compare different options by looking at the differences in life cycle costs. These differences can be directly tied to the features that are expected to differ among the various options. The best option will be the one that is expected to have the greatest reduction in LCC from the base case. Note that the LCC is expressed as an annuity (i.e. as an equivalent annual cost over the life of a project). Sensitivity analyses are generally conducted as part of life cycle cost evaluations to attach critical values for sensitive input data. The discounting rates depend on the service life of the project calculated. Discounting rates of a maximum of 5% net are generally in use for service lives of 30 and more years.

One of the most important figures within LCC is the service life. Unfortunately the service life is not a given fixed value, but is influenced Figure 2: Implementation of under sleeper pads at Austrian Federal significantly by the initial quality and the Railways maintenance executed.

72 JOURNAL OF PROCEEDINGSTECHNICAL

Furthermore, it must be differentiated between the technical and the economic service life, as the technical service life can be increased by expensive maintenance actions as single sleeper exchange or by limiting the operation in speed and/or axle load. However, this must not be the target as it leads to high costs and poor performance. The economic service life is the time span resulting in the annual cost. The economic service life is reached as soon as the additional maintenance necessary to prolong service life is more costly than the reduction of depreciation due to the prolonged service life.

It can be mathematically proven that the ratio of the maintenance intervals is indirectly proportional to the that of deterioration rates. In other words, this means that a halved deterioration rate leads to a doubled interval for tamping actions and points out the importance Figure 3: Analyses of track behaviour over time of the rate of deterioration. Furthermore, research has shown, that increasing maintenance cycles due to high quality leads to a remarkable increase of service life. However, if the maintenance level is reduced leading to poor quality, service life will be shortened. These effects depict the overwhelming importance of track quality, namely the initial quality and the deterioration rate, for service life, maintenance demand and thus the life cycle cost of track.

RESULTS COMPARING STANDARD TRACK AND TRACK WITH UNDER SLEEPER PADS

As the deterioration rate differs widely due to the various boundary conditions, comparing track with and without USP requires comparing these two types of ballasted track facing the same boundary conditions. Elastic footings for concrete sleepers have been under Figure 3a: Reduction of ballast contact pressure with USP investigation for quite a long time throughout Europe. It is obvious from the test results that track deterioration is reduced dramatically due to the use of Under Sleeper Pads (figure ).3 The general results showed that:

• the initial quality is increased by 18 per cent • the tamping cycle can be prolonged without loss of quality in a range from 2.00 to 3.00 • the service life should increase by more than one third

The initial quality of USP tracks is better than that of conventional tracks as the initial settlements of track are reduced and with reducing these settlements to their absolute differences, the initial errors are reduced automatically.

This data forms the input data for calculating the economic efficiency of USP. The calculation is based on Austrian cost figures. The additional cost of USP is 30% of sleeper costs including fastenings. In order not to Figure 4: Internal rate of return for the additional investment into under associate the results to a specific cost, level sleeper pads numerous sensitivity analyses have been

73 JOURNALTECHNICAL OF PROCEEDINGS

Figure 5: Development of track quality

carried out in varying specific cost data. Durability of track increases as the critical Elastic sleeper pads with vibration isolating The economic evaluation shows that this element of the ballasted track, the ballast, characteristics are a very effective measure for reduction leads to enormous savings in faces lower loads. reducing secondary air-borne noise. Since the terms of total LCC justifying the relatively low vibration and sound emissions of the railway additional investment cost. However, savings In Austria, concrete sleepers are the cheapest track are also significantly dependant on the are higher, the higher traffic loads are figure( solution for the available investment, concrete quality of the superstructure, the more even the 4). Therefore, the Austrian Federal Railways sleepers with Under Sleeper Pads are the superstructure is, the lower the emissions are. (ÖBB) started to implement USP equipped same price as wooden sleepers. However, In addition to this effect, the physical principle concrete sleepers as a standard solution on cost of track renewal increases by 5%, service of vibration isolation plays a big part in the highly loaded tracks (more than 30,000 daily life is prolonged by more than one third and reduction of emissions. The performance of gross tons per track), sharp curves (less than maintenance can be reduced down to 50% a vibration isolation solution is dependent on 600 m), high speed (more than 160 km/h), and (average values for track on good sub-soil with factors like overall mass, stiffness and system turnouts, first. proper dewatering systems). These facts result damping. By means of inserting an elastic in an average reduction of total life cycle cost element such as USP, an oscillating system is As further results for other boundary conditions by one third. created. (e.g. curved track) are also published in the UIC leaflet, in the following additional results VIBRATION ISOLATION WITH In the best case the frequency of the system is regarding initial quality, quality after tamping UNDER SLEEPER PADS way below the spectrum of exciting frequencies and expected service life will be discussed, that should be isolated. This is based on the based already on more than 60,000 cross While USPs are excellent for reducing principle of the one mass one spring single sections compared. shows typical Figure 5 maintenance costs, which has been already degree of freedom oscillator. The dynamic track quality behaviour for a section of 54,000 outlined in detail, they are also a cost efficient stiffness of the USP used must be tailored gross tons per day and track, on the left side and effective measure for reducing vibrations to the specific installation situation and the conventional ballasted track with rails 60E1 on and secondary air-borne noise next to constraints of the project. Only if the technical conventional concrete sleepers, on the right solution is carefully engineered will the USPs ballasted track superstructure (refer to figure hand side the same superstructure but with be able to exploit their full vibration isolation 8). Highly elastic pads offer a simple method USP. The vertical red line shows the time of for reducing vibrations on railway lines that performance. renewal, the green line a tamping action. is cost effective in comparison with Under Ballast Mats (UBM). In addition, they exhibit VALIDATION OF VIBRATION However, this is just a specific result. all the positive properties of elastoplastic USP, ISOLATION WITH USP Therefore, in the quality after tamping figure 6 such as an increase of contact area and thus and the deterioration rate is given for all reduction of LCC. The vibration attenuation performance of checked sections. The quality deterioration elastic elements in the installed state is rate is reduced from 0.14 to 0.07 as was One advantage of USP over UBM is, that generally quantified by the insertion loss. expected by the theoretical calculations. The retrofitting can be executed a lot easier with The insertion loss describes the relative quality after tamping is reduced from 0.5 mm USP, as sleepers can be exchanged one by performance of an attenuation solution standard deviation to 0.3 mm. As the analyses one. Installation of UBM in an already existing compared to a reference situation, answering are based on Austrian data, all tamping actions track would be a lot more complex and costly. the question of how the one-third octave bands were stabilised. The vibration attenuation performance of of the structure borne noise change after UBM is of course higher, due to the full- installing USP. To enable this comparison, a These results underline the technical and surface decoupling, the bigger mass and ceteris paribus principle should be followed: consequently the economic efficiency of Under the lower stiffness of the elastic layer. The the train, the speed, the roughness of the rail Sleeper Pads. Figure 7 summarises the decision between USP and UBM is a trade-off and other parameters shall ideally be the exact characteristics of wooden sleepers, concrete between total cost (product plus installation) same or at least very similar to make a valid sleepers and concrete sleepers with Under and attenuation performance and has to be insertion loss calculation possible. Sleeper Pads. The durability of the concrete taken on the basis of project specific boundary sleepers stays the same, the lateral track conditions. Depending on the maximum permissible rail resistance is increased as the ballast stones deflection, padded sleepers achieve insertion can press into the pads. losses in the order of 10 dB(v) to 15 dB(v) (at 63 Hz). 10 dB(v) of reduction are equal to an

74 JOURNAL OF PROCEEDINGSTECHNICAL

which are ideal for effectively minimising vibrations. Deliveries were made both to the CEMEX sleeper works and directly to London Underground. This renovated section of the District Line runs through very narrow tunnels, meaning that there is little or no gap between the sleepers and the drainage channels adjacent to the tunnel wall. A particular challenge in this case was preventing an increase in the level of sound transmission through the tunnel walls. The elastic Sylodyn® bearings were for the first time placed not only on the bottom of the sleepers, but also on the ends (refer to figure 10), thus reducing the transmission of noise and vibrations through the tunnel wall.

Around 7,000 pads for concrete sleepers and roughly 1,000 pads for timber sleepers were used on a stretch of track extending over approximately 2.5 kilometres. CEMEX fitted the elastic bearings to the concrete sleepers directly in its sleeper factory. London Figure 6: Impact on quality and track deterioration by installing USP Underground itself fitted the pads to the timber sleepers.

Structure-borne noise measurements taken following the installation verify the effectiveness of the vibration protection solution. “A significant reduction in groundborne vibration has been achieved in a number of neighbouring properties. Some long-term residents living next to the track have even written and thanked us for providing them with greater peace and quiet”. Additionally, the sleeper pads supplied by Getzner required no changes to the installation programme, methodology or equipment for the track renewal. “Overall, the use of Getzner sleeper pads on this project has been a great success”, stated Mike Barlow, Principal Project Engineer from London Underground. Figure 7: Characteristics of ballasted track with different types of sleepers Other successful vibration isolation projects with USP in the UK include the Birmingham isolation performance (reduction) of 69%! PROJECT EXAMPLE: LONDON Arena Tunnel and numerous projects with Secondary air borne noise arises due to the UNDERGROUND turnouts and other track sections with special sound emission of a structure that is stimulated requirements. to vibrate, for example by a passing train. The track of the London Underground District This applies in particular to metal structures, Line was completely renewed between SUMMARY such as steel bridges and viaducts. Paddington and High Street Kensington stations. Around 173 million passengers use Under Sleeper Pads are a state-of-the-art Measurements in track comply with the this line every year. Starting in July 2011, this technical solution reducing both lifecycle theoretical calculations based on the very busy section of track, which is also part costs as well as reducing vibrations in railway impedance model. Most recently a railway of the Circle Line, was upgraded with new tracks. Being already a standard product in track in Poland was assessed by experts from ballast, rails and brand new sleepers with pads countries like Austria, Germany, France and Wroclaw University of Technology and the supplied by Getzner Werkstoffe. The sleeper Italy, in recent years the positive effects of USP R&D department of Getzner Werkstoffe. The pads protect the track superstructure and demonstrated also led to introduction of these dominant one-third octave band of passing reduce the level of vibrations caused by the elastic elements in the UK. trains can generally be found at 63 Hz. The underground trains. use of Sylomer® USPs resulted in an insertion As of 2018 more than 200.000 sleepers in the loss of 11.6db(v), which is equal to an average They also have a beneficial effect on the UK (mainline and urban railway) have been vibration reduction of 74 per cent. Vibrations numerous dwellings alongside the track, as the equipped with polyurethane USP. The biggest are reduced at frequencies above 31.5 Hz decrease in vibrations noticeably improves the number of these USP have been installed for compared to the track without any elastic residents’ quality of life. LCC reduction reasons; a smaller number for elements. In the range of the natural frequency vibration isolation purposes. This development only a very small resonance amplification could Providing elastic bearings for this stretch of can also be observed worldwide, as the be observed. These investigations, especially the District Line was the first major sleeper adoption of USP into best practices for railway at the relevant frequency range of 63 Hz, pad project for London Underground: the superstructure construction continues to demonstrate the fundamental suitability of USP vibration protection requirements called for spread across all continents. in reducing vibrations and secondary airborne the use of full-surface Sylodyn® sleeper pads, noise.

75 JOURNALTECHNICAL OF PROCEEDINGS

To sum up all theoretical calculations and practical experiences, it can be stated that only concrete sleepers with Under Sleeper Pads fulfil the demand for a more sustainable and cost effective superstructure.

FURTHER LITERATURE

Veit, P.; Marschnig St.: Under Sleeper Pads – Economic Evaluation, TU Graz, project report for UIC working group, 2012

Veit, P.; Marschnig, St.; Berghold, A.: WINS – Wirtschaftlicher Nutzen von Schwellenbesohlungen, project report for Austrian Federal Railways, 2010, Graz

Marschnig, St.; Berghold, A.: Besohlte Schwellen im netzweiten Einsatz, ZEVrail, 2011, Berlin

Auer, F.: Zur Verschleißreduktion von Gleisen in engen Bögen, doctoral thesis, 2010, Graz Auer, F.: Der Einfluss von elastischen Figure 8: Vibrations and structure-borne noise in the surroundings of Komponenten auf das Verschleißverhalten railway lines von Gleisen in engen Bögen, paper at 39th Conference Modern Rolling Stock, 2010, Graz Loy, H; Combating structure-borne noise and vibrations by putting pads on sleepers – their effect and limitations, ETR Austria, December 2012

DIN 45673-3: Mechanical vibration – resilient elements used in railway tracks – Part 3: Experimental evaluation of insertion loss of mounted track systems

Loy., H; Kwiatkowska, E.; Biskup, M; Measuring the vibration-isolating effect of an elastic railway superstructure in Poland, Global Railway Review, Volume 24, Issue 1, 2018

Potocan, S; Vibration protection for Birmingham’s Arena Tunnel, European Rail Technology Review, 2011

Figure 9: Measured insertion loss curve of superstructure with USP in Krakow, Poland

Figure 10: concrete sleeper with USP including a special elastic bearing on both front ends of the sleeper for additional vibration isolation (left: schematic 3D image, right: photograph).

76 JOURNAL OF PROCEEDINGSTECHNICAL

Optimisation of the AUTHOR:

Andy Vickerstaff wheel rail interface Transport for London on London Underground

ABSTRACT These are single lines within each tunnel The loss of Saturday nights is especially and are ballastless in construction. This difficult as, due to the later start of operations London Underground faces an enormous was possible due to the introduction of on a Sunday morning, this shift could be nearer challenge to run a modern metro service in electric traction reducing the requirement for to 5 hours compared to 3 during the week. excess of 40 million gross tonnes per annum ventilation. on Victorian infrastructure. Line upgrade Management of the wheel-rail interface, projects have invested in rolling stock and Although the deep tube lines no longer within the already challenging constraints signalling to meet modern demands but required the road to be removed for placed upon us by the infrastructure, is further investment in the infrastructure has remained construction, they were required to be built to challenged by spending across both renewals within a separate track renewals programme. follow the same route underground. It is this and maintenance being reduced due to the The removal of central funding in 2019/20 requirement that explains the unique geometry removal of the central operating grant in 2019. will lead to reductions in spending in this which leads to some of the greatest wheel- Therefore, it is even more imperative that programme along with maintenance. In order rail interface challenges. For example, where we understand the failure rates of the assets to meet this challenge, optimising the wheel- the Central line runs between Liverpool St involved so that preventative maintenance rail interface is essential to reduce costs and and Bank, it follows the line of the medieval regimes can be implemented that ensure minimise risk. Preventative wheel turning, Threadneedle St, and consists of a series of maximum value for money and an increase in accurate predictions of rolling contact fatigue, 100m reverse curves. This includes through reliability. and appropriate adhesion management are all the platforms and leads to the synonymous essential to achieving this goal. ‘Mind the Gap’ phrase associated with the PREVENTATIVE WHEEL Tube. TURNING INTRODUCTION The earliest line which was exempted from The increase in tonnages seen by the this requirement was the Victoria line, when it London Underground (LUL) is the oldest infrastructure is caused by running more trains, was first opened in 1968 with no curves below underground metro service in the world, the more frequently. Therefore, from a rolling 400m in radius throughout. However, it was still first section having opened between Baker stock perspective the same effect is seen in constructed in bullhead rail despite this being Street and Farringdon on 10th January 1863. the increase in the kilometres run per annum. phased out on the mainline by this time. It was Initially construction of the tunnels was carried Wheel turning has been treated as a reactive also the first Automatic Train Operation (ATO) out utilising the ‘cut and cover’ technique maintenance activity whereby wheels were railway in the world and since its upgrade in whereby the roads were dug up, the railway turned upon discovery of defects during visual 2009 it now runs with a train every 90 seconds. built within the excavation the brick arch underframe inspections. Whilst the least curvaceous of our lines it is still tunnels built over the top, and finally the road remains a challenge due to running in excess re-built on top. They were also built with some The profile is measured using a maintenance of 40 million gross tonnes (MGT) per annum. provision for ventilation as the services were gauge first, whereby if contact was made at a being provided by steam locomotives. Both number of points then the wheel would have The sub surface lines are currently being lines were located within one tunnel and were failed for flange height, flange thickness or upgraded as part of the 4 Lines Modernisation of traditional ballasted track construction. wheel hollowing. This gauge was set for each (4LM) programme to increase the services fleet based on its wear rate for the exam during in the core sections to 32 trains per hour. These lines are still referred to as the which it was used, (typically 14 or 28 days), The trains have already been replaced with sub surface lines which encompass the so that wheel turning could then be planned the more modern S-Stock and the signalling Metropolitan, District, Hammersmith and City before the next exam. upgrade will eventually allow Automatic Train and Circle line services, approximately 40% Control (ATC) to deliver the increased train of the network. Since 1890 with the opening If the wheel failed the maintenance gauge frequency. Since 2011 the tonnage on the core of the City and South London railway between then the safety gauge was used which would section has already increased by 45%, and Stockwell and King William Street, (now part determine if any of the parameters were once ATC is implemented it is predicted this of the Northern line) tunnels were built as beyond the standard and the wheel required will increase by 81% to nearly 50MGT. deep tube lines. These were far less intrusive immediate turning. However, these gauges are and much cheaper to build but due to the not attached to the wheel and therefore no set The introduction of Night Tube in 2016 has led difficulty of construction they were built as datum is used and there is a wide variety of to increases in tonnage, even where upgrades small as possible and are approximately 3.6m interpretations between individual inspectors. have yet to take place, as well as removal in diameter. of access for maintenance on Friday and Saturday nights.

77 JOURNALTECHNICAL OF PROCEEDINGS

The increased requirement for train availability are in service. Figure 3 shows the distribution to meet the increased timetables means of wheels in service for the 09TS both before that maintenance planning can no longer be and after the implementation of a preventative based on a ‘run to fail’ policy and requires a turning regime. This is especially important preventative maintenance regime to ensure when attempting to carry out vehicle dynamics trains are available for service. Aligning modelling of rail performance, as will be seen maintenance frequencies as closely as later. possible also ensures that the number of times a train is out of service during its lifecycle is RAIL DEFECTS kept to a minimum. LUL aims to continually reduce the number of A network wide wheel profile monitoring rail defects, despite the tonnage increases, Figure 1: 4mm hollow treads (red) project was launched by the Wheel Rail through the introduction of better non- from new LT5 (blue) Interface (WRI) team using a Miniprof™ to destructive testing (NDT) techniques and ensure maximum accuracy of measurements analysis. B-Scan ultrasonic testing was and enable a preventative wheel turning introduced as it is recordable, which allows regime to be implemented for each fleet. The analysis to be undertaken off line and be principal mode of failure has been shown auditable if required. to be hollowing treads leading to a loss of conicity. Figure 1 shows an example of the An Ultrasonic Inspection Interval Programme worst wheel profile which was found on the (UIIP) was also introduced which sets the 09TS which operates on the Victoria line. interval between testing as a function of the The standard requires wheels to be no more tonnage and historical rail defects occurring than 2mm hollow, as this represents the point in the area. The maximum testing interval at which conicity is lost and wheels are no allowed in any area is 6MGT, but it can be as longer capable of steering through curves. The low as 3MGT in defect prone areas where this example shown in figure 1 is 4mm hollow. equates to a 28 day interval. Figure 2: Rate of hollowing for 09TS

It was clear from the initial analysis that The B-Scan traces have shown that cracks the manual inspection methods were not can develop from being undetectable to 20mm identifying wheels that were beyond the deep within this period. By utilising these standard and on the Victoria line it was techniques, numerous emergency defects, identified that this was due to an incorrect work where speed restrictions and clamping would instruction which called for the use of a feeler be required, have been prevented. However, gauge in conjunction with the safety gauge broken rails still occur as can be seen in figure and therefore staff were using a 4mm limit 4. Broken rails have averaged around 11 per rather than 2mm. When the fleet data had been annum since 2011 but appear to have reached collected a clear linear trend was established something of a plateau. It can be seen that the for hollowing, however there were clearly two lines which most frequently suffer broken rails different regimes as can be seen in figure are the Piccadilly and Northern lines. This is 2. The trailer cars (12 cars) showed a much due to them being the lines which still contain higher rate of hollowing than the rest of the the highest proportion of jointed bullhead rail Figure 3: Wheel profile distribution train where the axles are motored. in plain line, approximately 37% each from the for 09TS latest asset databases. Broken rails by type The 09TS uses both rheostatic and (flat bottom or bullhead) can be seen in figure regenerative braking, whereby the traction 5. This shows the discrepancy in rail types motors are used to provide braking force, and whereby although approximately only 40% of return this energy to the traction current supply. the network remains in bullhead rail it accounts However, as the trailer cars have no motors for 90% of the rail breaks. The rail breaks they rely purely on friction braking, which on which have occurred in flat bottom rail have all LUL trains is provided by tread brakes. This generally been related to weld porosity or failed resulted in two different turning regimes for the flash butt welds, rather than being related to 09TS with the trailer wheels being turned at the defects caused by fatigue failures caused 140 and the motor cars at 280 kilometres. This during service. has major implications for the overhaul strategy of the train as it has to be taken out of service The biggest source of bullhead broken rails is to have its wheels replaced on only 2 of 8 cars, related to foot initiated defects, typically from before repeating the process to replace the fishplated joints. An example can be seen in wheels on the rest. figure 6 where fretting between the rail and Figure 4 Broken rails since 2011 fishplate at the foot of the rail has led to a crack Changes to the train maintenance regimes to reaching the bolt hole and ultimately leading to encompass wheel turning as a routine activity the break. have ensured that wheel lathe demand can now be predicted. This allows for periods of These defects are almost impossible to detect reduced activity to be built in during the autumn ultrasonically because they occur from the when less predictable wheel flats occur, and fishing surfaces which cannot be inspected also for wheel lathe maintenance to take place. and they can quickly propagate to the bolt holes, and fast fracture. Therefore, the only From a wheel-rail interface management method of preventing these defects is visual perspective it allows us to understand at any inspection. given time what distribution of wheel shapes Figure 5 Broken rails by rail type

78 JOURNAL OF PROCEEDINGSTECHNICAL

The majority of bullhead sites remain within the it consists of sections on concrete sleepers, deep tube, as these are the most difficult and without check rails applied, and sections with therefore it is expensive to carry out track re- check rails on timber sleepers. Following construction. Visual inspection is carried out at renewal, the rate at which the rails were being night in the limited engineering hours window, damaged through both RCF and corrugation with limited lighting making them very difficult was higher than previously experienced at this to identify without removing the fishplates. site by the maintainer. An example of the type of damage can be seen in figure .9 A recent study conducted to look at the frequency of basic visual inspections has A sample of train speeds were downloaded via identified that across LUL the risk of a broken the Train Data Recorder (TDR) fitted to every rail in bullhead is 16 times greater than in S-Stock train, which are currently manually flat bottom. This risk along with a reduction driven. As expected it was shown that very few in spending on track renewals has led to a trains ever reached the Driving Technique (DT) change in strategy, where converting bullhead speed of 45kph, with a significant variation as sites to flat bottom is now the priority rather can be seen in figure 10. than full re-conditioning. When the layout of the site and the principles Rail defects have gradually been reducing of fixed block signalling are considered, the since 2013 before an increase in 2017/18 speed patterns which are seen in figure 10 as can be seen in figure .7 Emergency are not unexpected. Trains leaving Farringdon rail defects, those which result in a speed station are driving around a blind corner and, restriction being applied, have been reducing given the radius of curvature, cannot be sure mainly due to the introduction of B-Scan which whether A227A will have a green aspect, Figure 6: Typical rail break from has enabled defects to be found before they hence the use of repeater signal R227A which fishplate fretting reach emergency status. The increase in will tell the driver the status of the next actual 2017/18 was caused by a failed grinding trial signal. which reduced the amount of material removed from the railhead. This proved to be insufficient A similar situation occurs at the next signal to remove the martensite layer in which squat A227B, for which a repeater is also placed type defects1 can develop. This is by far the at A227A. Driving instructions for fixed block most common defect found on LUL as can be signalling is based on a line of sight principle, seen by the proportion of defects found on the whereby until a driver can identify the next Central and Jubilee lines in figure .7 These signal is clear they should proceed with defects only occur in open sections, where caution. The kind of patterns seen in figure adhesion conditions can be low enough to 10 can be explained by drivers reaching the cause wheel slip protection (WSP) activation in repeaters and knowing the next signal is not rolling stock with Alternating Current traction clear, and therefore driving at reduced speed packages. The sub surface lines are also now so that they will not need to brake as severely beginning to suffer from this type of defect, should the signal not clear by the time they although not yet in the concentrations seen reach it. This would be no different to the on lines where ATC is already implemented average car driver who would drive slowly Figure 7: Rail defects by line (Central, Northern & Jubilee). between series of traffic lights, knowing that there was nothing to be gained in journey These concentrations are caused both by the time by increasing their speed between fixed train typically stopping in similar locations, stopping points. Depending upon how the final major junctions where trains can be held for logic of the ATC system is implemented this example and because ATC cannot adjust its may or may not change the speeds as moving style as well as manual drivers who implement block systems can still allow trains to move earlier braking at a lower rate to adjust for low forward, just at a slower speed to maintain adhesion conditions. separation. However, until this is implemented the track will experience significant under FARRINGDON TO BARBICAN speeding through the section resulting in cant efficiency for the majority of speeds as can Farringdon to Barbican on the Hammersmith be seen in figure 11. Although this site has and City line was renewed in February 2016 been significantly over canted in order that it is in order to remove a section of bullhead rail, suitable for future potential speeds; designing and also allow for a double junction to be for cant deficiency is especially challenging on Figure 8: Farringdon to Barbican added later. This junction is required to allow LUL given the constraints. trains to enter the new sidings currently under construction which are required in order to The relatively short inter-station sections in operate 32 trains per hour. This site has been central London ensures that for a given section intensively monitored since its installation for of track the difference in speed between the rail profile and condition as part of a wider front and back of the train can be enormous. rolling contact fatigue (RCF) study. This site On ATO lines, designers have to design for reflects the challenges faced across LUL the actual train driving speed as well as a in optimising the wheel-rail interface. The Maximum Attainable Speed (MAS) which is designed train speed profile, along with the the speed the train can reach given a fault current signal layout and gradients can be seen in the signalling system. Finally, there are in figure .8 The radius of curvature through the limitations of platforms, which are often the site varies between 160 and 250m, and curved, where there is an even greater range Figure 9: Rail condition at signal R227A

79 JOURNALTECHNICAL OF PROCEEDINGS

of speeds which must be accommodated This is not only expensive and environmentally due to braking and acceleration as well as damaging, it also requires a change in track managing the platform train interface. Due to stiffness, often within curves such as this site, the deterioration of the rails, the high rail was which introduces a higher risk of geometry replaced with British Steels premium rail steel faults and potential for broken rails. This study High Performance (HP) 335 which had recently concluded that the majority of LUL stocks been approved. The rails performance at the derailment risk does not significantly change same location can be seen in figure 12, which above 140m in radius where the rate of change shows the rail photographed under Magnetic of cant is lower than 30mm/sec, even with Particle Inspection (MPI) to highlight the RCF. safety standard geometry faults for twist.

Figure 12 shows that in 260 grade steel RCF This site could have been installed without the had already developed in the centre of the need for a check rail, thus reducing the costs of Figure 10: Actual train speeds railhead within 18MGT of installation, whereas installation and maintenance. in HP335 some much smaller RCF cracks are only starting to appear at 37MGT. The sites will ROLLING CONTACT FATIGUE continue to be monitored. The site has recently been ground, so it will be possible to establish In 2013 LUL introduced the Rail Surface Crack the depth of RCF cracks in the railhead. Measurement (RSCM) system manufactured by MRX Technologies. This measures the Since this site was renewed an intensive study depth of RCF through magnetic flux leakage, was undertaken by LUL to determine more rather than interpretation of the depth from accurately the radius at which check rails are the length of surface cracks. Changes to required to mitigate the derailment risk using the standard were also made and required Vampire™, vehicle dynamics modelling. LUL re-railing at a depth of 5mm or greater as this standards currently require check rails to be could not be removed through rail re-profiling. installed where the radius is less than 200m. One of the driving factors behind this research, This resulted in approximately 20km of re- was that at the time there was no check rail railing being carried out across the network. It baseplate available that didn’t require the was hoped that by using this system it would Figure 11: Actual cant deficiencies installation of timber sleepers. be possible to establish growth rates of RCF and therefore determine the correct frequency for rail re-profiling to be carried out to prevent RCF. However, it is not sufficiently accurate in the first 1-2mm of depth, when it would be practical to remove by rail re-profiling in the time available within engineering hours. Therefore, an intensive monitoring regime was introduced, either on sites which were renewed such as Farringdon to Barbican, or in areas where re-railing had been carried out for RCF following the initial introduction of RSCM where the date of re-railing was known.

The sites are monitored for rail profile using a Miniprof™ as well as being photographed under MPI to enable the cracks to be seen more easily. Approximately 60 sites have been included in this study which covers all different rolling stocks and a variety of rail types and curvatures between 70 and 1000m. By monitoring the rail profile, it enables us to Figure 12: Rail condition Farringdon to Barbican in R260 and HP335 establish wear rates and accurately model the sites using Vampire™ to validate our RCF against the Whole Life Rail Model (WLRM)2.

The sites which have been monitored have been classified as either having no cracks, cracks, or breaking out, as can be seen in figure 13. The third case where the surface of the rail is breaking out is a key limit for rail re-profiling on LUL, as although these cracks often have limited depth they can be classified as Ultrasonically Untestable Rail (UUR). The results of this study can be seen in figure 14 where a very simple model has been developed by plotting a logarithmic best fit line for a minimum rail re-profiling frequency, where cracks have developed, and a maximum, where the rail has started to breakout. This Figure 13: Visual classifications l to r: no cracks, cracks, breakout includes both high and low rails within the

80 JOURNAL OF PROCEEDINGSTECHNICAL

Figure 14: Rail re-profiling frequency model

Figure 15: Low rail RCF bands

rolling radius difference to steer through the The WRLM can be used to demonstrate the curve without generating flange contact. importance of cant deficiency for reducing RCF However, because this curve is very tight, damage. Figure 19 shows the WLRM damage and the wheelset is constrained by a check factors for the site when run at constant speeds rail, steering is by check and flange contact. of 20, 30 and 40kph for the trailing axle. Therefore, the contact position is purely a function of the shapes of the wheels and rails. The higher the cant deficiency, the more Figure 16: Contact positions for low lateral force will be generated at the trailing In figure 16 the contact position for the 2mm axle which will result in a greater rolling radius rail at 53 and 58MGT hollow tread at 53MGT shows that it is moving difference because of the lateral shift of the between two contact positions, due to the wheelset. This in turn will reduce the creep classification as it would not be efficient to amount of hollowing and showing how the forces generated at the wheel-rail interface, only re-profile one rail. Based on this model vehicle is becoming dynamically unstable due which in this case will reduce the RCF damage LUL would have to undertake 110km of rail to the loss of conicity at this level. in the centre of the railhead. re-profiling per annum. This model will be developed further by accurately modelling The RCF on the high rail has already been In this curve it does not result in any greater the sites in Vampire™ to predict the range of shown to reduce the rate at which it has force being generated at the leading axle as it contacts across the railhead and the forces developed when R260 was replaced with is already in flange contact, along with being which are being generated at the wheel-rail HP335. One of the developments of the held by a check rail, and therefore it continues interface. This is possible because the rail WLRM3 was the changes which should be to operate in the wear region. profile is known and an accurate distribution of made for the use of this premium rail steel the wheel profiles which are being run across which can be seen in figure 17. HP335 has worked well since being installed it. The Farringdon to Barbican site has been in this site but unfortunately it has not worked modelled using the rail profiles collected at a The WLRM is based on the propensity to as well in all locations. Since HP335 was variety of tonnages with the range of wheel develop RCF being a function of the Tᵧ which approved for use on LUL, approximately 7km profiles known to be in service. The results of is a measure of all the energy in the contact of rail has been installed across the network, these simulations show how initially one band patch. It has four separate areas, below 15J through both renewals and maintenance. It has of RCF develops near the gauge corner (green) where no RCF can be generated, between 15 principally been used within sites which have before a second band develops nearer the field and 65J where RCF is generated, 65 to 175J suffered from high wear, corrugation, or RCF side (red) as can be seen in figure 15. where both RCF and wear are generated, rates. and greater than 175J where only wear is The results from the simulations show the generated. In February 2018, a broken rail was discovered contact position for the range of wheel profiles in an HP site on the Central line, between as a function of hollowing (0, 0.5, 1, 1.5 and Based on the material properties for HP335 Liverpool St and Bethnal Green. It was the low 2mm) for the leading axle with rail profiles this pushes the peak of the triangle to the rail of a 400m radius curve, which was installed taken at 53 and 58MGT in figure 16. The right with a shallower gradient, and therefore on Pandrol Vanguard resilient track fixings, due y-axis is the distance through the site where a higher Tᵧ at which wear is generated. to this being a site which is particularly prone rail profiles have been taken at positions 140m Therefore, there are sites where should HP335 to rail corrugation. The rail had accumulated and 260m. be installed it would potentially move from wear tonnage of 19MGT. to RCF generation, or increase the rate of RCF The contact positions show that all the wheel generation. The rail had broken from an RCF crack in the profiles at 53MGT (left) are near the gauge centre of the railhead which had propagated corner (gauge corner being at 0 and contacts The RCF which was being generated in the 23mm into the railhead before fast fracture had being negative for the left rail), but at 58MGT high rail between Farringdon and Barbican occurred as can be seen in figure 20. the distribution of contacts is much wider (figure 12) can be shown by the WLRM to be (right), but is also further from the gauge developing wear from the leading axle and In April 2018, a series of 13 cracks of corner. This is because the low rail is losing RCF from the trailing axle. When the WLRM approximately 22mm deep were discovered its crown radius through wear and therefore factor for HP335 is used it shows that the over a distance of 2.5m in an HP rail site on the the contacts are becoming wider and further leading axle will still be generating wear, and District line between Cannon St and Mansion from the gauge corner. In a mild radius curve that the RCF rate should be reduced at the House. This was the high rail of the exit the contact point would be a function of the trailing axle as can be seen in figure 18. transition of a 200m radius curve installed on wheelset attempting to generate sufficient timber sleepers in ballasted track. The rail had

81 JOURNALTECHNICAL OF PROCEEDINGS

been in service for an accumulated tonnage of There is also a small band of cracks between 26MGT. Investigations are still be carried out, the areas of the wear and centre rail RCF in and no further installations of HP335 are taking the 200m example where some leading axle place until these have concluded, but the cracks are being developed (orange) as the rail fundamental issue is the direction of the RCF wears but these are unlikely to be generated at cracks which are being generated. In ‘classic’ 90 degrees to the surface due to the amount of RCF which is generated in the gauge corner, lateral force at this contact. Low rail RCF can the cracks typically form at 30 to 40 degrees be generated in curvatures below 1000m and to running surface. However, in the case of low therefore HP335 could only be installed above rail or high rail trailing axle generated cracks, this radius where it is unlikely it would provide the angle is closer to 90 as can be seen in a sufficient cost/benefit ratio as wear rates are figure 21. already sufficiently low at these radii.

When these samples were analysed in the ADHESION MANAGEMENT Figure 17: Whole life rail model for laboratory, the RCF cracks within them were 3 R260 and HP335 no deeper than 0.5mm, which is undetectable Adhesion management across LUL is by either ultrasonics or RSCM. Although the done through a combination of track based only samples looked at in this level of detail lubricators, a mixture of mechanical (figure have been HP335, the kind of dense crack 24) and electrical units, as well as on-board formation also occurs within 260 grade steel ‘stick’ systems (figure 25). On board systems and therefore the cracks are likely to be at a for gauge corner friction are fitted to the 92TS similar angle. (Central), 95TS (Northern), 96TS (Jubilee), 09TS (Victoria) and S-Stock (Sub Surface). Figure 22 shows the cracks from one of these Top of rail (TOR) on board sticks are also fitted samples demonstrating how, due to the density to 09TS, and will shortly be fitted to S-Stock. they can join up below the surface and result in the pitting and breaking out (figure 13), which Historically LUL suffered greatly from rail wear, Figure 18: Contact positions (left) often results in Ultrasonically Untestable Rail especially on the sub surface network when and WLRM damage factors (right) (UUR) in 260 grade steel. In HP335 it appears A, C and D-Stocks operated. These trains, more vulnerable to these cracks propagating to with the exception of D-Stock later in its life, fast fracture from such shallow depth. had fixed frame bogies which resulted in much higher wear at the wheel-rail interface. Rail The best performing sites where HP335 has wear was also easier to manage with bullhead been installed have either been installed as jointed rail, as rails could easily be changed part of renewals, where if on ballast they have and also transposed from low to high rail. been installed with under sleeper pads and tamped to design geometry, or within deep As track has been modernised to flat bottom, tube. Those which have failed quickest have continuously welded rail (CWR) changing rails been on Pandrol Vanguard followed by timber became a more expensive activity which led sleepers on ballast, installed by the maintainer to a concerted campaign in the early 2000s with only the rail being changed. This has led to install track lubricators and monitor the to the current conclusion that the vulnerability performance much more closely, leading to a to fast fracture from very light RCF cracks is a reduction in rail wear. However, as wear has function of the amount of vertical rail deflection. been better controlled RCF has become the Pandrol Vanguard has been installed to combat dominant failure mode. Figure 19: Reduction in trailing axle residential noise complaints by isolating the RCF with cant deficiency rail from the sleeper, and to achieve this it is Vehicle dynamic studies have enabled a much very vertically soft. Timber sleepers on ballast more accurate prediction of when flange would be the next softest track form on LUL, contact occurs and where gauge corner whereas the best performing sites are in lubrication is required. Although numerous concreted deep tube track. factors affect the precise location of flange contact it has been shown that above 600m Rail deflection is currently being measured in radius it cannot occur. On the sub surface in a range of sites to establish if it is possible network this has enabled approximately 50 to define a track stiffness for the installation lubricators to be removed from the network of HP335 which may include criteria such as once the final D-Stock has been replaced by sleeper spacing. If a clear correlation cannot the S-Stock. be established, then HP335 would only be installed in high rails where RCF could not be Top of Rail (TOR) friction modifier has also generated in the middle of the rail, and for low been used across the network specifically rails where it could not be generated at all. for wheel squeal, although it is now being considered for heavily corrugated sites. The For the majority of LUL stocks this would biggest benefit of the on-board TOR is that it is be a radius of above 300m for high rails. An always present when needed and will reduce example can be seen in figure 23 where the wheel wear rates. Unfortunately baseline wheel high rails of a 400m (left) and 200m (right) wear rates of 09TS prior to TOR being fitted radius curve can be seen. RCF is only being were not ascertained but for S-Stock this will generated in the gauge corner for the 400m enable benefits in increasing the preventative curve (green) whereas in the 200m only wear turn frequencies to be quantified. is generated in the gauge corner (blue), with RCF cracks in the centre (green). Figure 20: HP335 Broken rail

82 JOURNAL OF PROCEEDINGSTECHNICAL

The overall adhesion management strategy for LUL is to provide as much protection on board as this is easier to maintain, as sticks can be re-filled as part of routine underframe inspections and removes the requirements for track access, which is already being reduced by Night Tube. The next phase of this strategy will be to trial certain sites to ascertain at what radius, or curve length, will the on-board systems be sufficient to manage wear.

Track based solutions will always be required on the tightest radius curves which has been shown when lubricators have been left off following grinding and the noise is intolerable within hours of traffic starting. The on-board systems also give no protection to the back of the flange and therefore check rails will still require track based lubrication.

NOISE AND VIBRATION

Noise and vibration are issues for all railways, especially urban ones. The biggest issue for LUL is vibration transferred from deep tube Figure 21: Gauge corner (left) and railhead centre (right) cracks lines to residential properties, typically caused by rail corrugation. On LUL this has often led to reactive rail grinding taking place, not under the direction of engineering. However, since noise and vibration were raised as a potential risk to Night Tube operation, far more engineering resource has been directed to reducing it.

Rail grinding has been shown to only reduce noise in properties between 2-3dB, and its effect only lasts 4 to 6 weeks on high tonnage lines such as the Victoria Line. Rail grinding at this frequency is neither practical nor cost effective, as it is treating only the symptom and not the root cause. One option which has been used to reduce the vibration being transferred to properties is the Pandrol Vanguard system (figure 26). This suspends the rail in resilient rubber mountings and isolates the rail from the ground, meaning the vibration cannot be transferred to properties and has resulted Figure 22: Sub surface cracks in HP335 in reductions of up to 15dB. Unfortunately, it has also lead to an increase in the noise experienced by passengers and train operators as the energy being generated has not been damped.

Therefore, it is not necessarily the appropriate solution. A lot of work is now going into understanding the root cause by identifying the frequencies of corrugation and whether these align with pinned-pinned resonance as a function of train speeds and sleeper spacings4.

The 92TS on the Central line appears to be particularly prevalent to generating extremely deep rail corrugation especially in sites where NTF415 deep tube concrete sleepers have been used. Initial work has shown that at a number of sites for the given speed and sleeper spacing there are significant undamped frequencies which could be the root cause of the severe corrugation.

Figure 23: High rails of 400m (left) and 200m (right)

83 JOURNALTECHNICAL OF PROCEEDINGS

CONCLUSIONS This will be corrected following the change demand on historical infrastructure. However, in grinding strategy in January 2018. The by implementing a wide-ranging study to Optimising the wheel-rail interface on London serious defects are dominated by failures at understand the degradation rates of the key Underground is an enormous challenge but joints within bullhead rail, whilst due to the assets it has been possible to demonstrate the one that is essential to operating a modern introduction of B-Scan more defects are found preventative maintenance regimes which are metro service on Victorian infrastructure. early enough to enable repairs to be carried required to reduce the whole life cost. out without the need for re-railing or the Preventative wheel turning has now been imposition of speed restrictions. For the first time in LUL history the implemented across all fleets and ensures that specification for the Deep Tube Upgrade concity is maintained for all wheels in service. RCF is now the dominant failure mode of rails Programme rolling stock contained specific It has also driven a change in culture within on LUL, replacing historical issues of wear. The clauses related to track damage. The fleet management that treats wheel turning as WLRM has been shown to give reasonable understanding of how the wheel-rail interface an essential preventative maintenance activity. predictions of the curvatures which are most on LUL can be optimised will ensure a smooth It is essential for managing the interface vulnerable to RCF. The rates of growth for transition on these lines to a world class that the distribution of wheels in service is depth is still the biggest remaining question service. understood so that RCF damage on rails can and an area where further research is required be accurately predicted. across the industry. ACKNOWLEDGMENTS

Rail defect numbers have been falling for a However, if the preventative rail re-profiling The results presented in this paper have number of years, with the exception of 2017/18 strategy continues to be delivered in been possible due to the efforts of a team of due to the increase in squat type defects. engineering hours then it is not feasible to engineers which form the wheel-rail interface remove more than 1mm across the railhead. team alongside the author. My thanks for their The majority of sites which have been ground continued dedication to Matthew Lee, Christine within the monitoring programme have rarely Baldwin and Dennis Johnston-Webber. required more than 0.5mm to be removed from the railhead but RSCM does still identify sites REFERENCES where RCF is greater than 5mm deep. [1] S.L. Grassie, D.I. Fletcher, E.A. Gallardo Understanding the factors which lead to these Hernandez, P. Summers: Studs: a squat type depths of RCF remains a challenge. Subtle defect in rails, Proceedings of the Institute of geometry changes, which could be caused by Mechanical Engineers, Part F: Journal of Rail misaligned welds or joints and changes in track and Rapid Transit, 31st October 2011 stiffness are the next areas of research which LUL will develop. [2] M. Burstow: Whole Life Rail Model application and development: Development HP335 rail has been proven to have the of a rolling contact fatigue damage parameter Figure 24: Traditional mechanical potential to increase rail life by up to 4 times (Burstow report) in some of the most challenging areas on lubricator AEATR-ES-2003-832 Issue 1, October 2003 LUL. However, it has also been shown to be vulnerable to causing serious rail defects [3] P. Molyneux-Berry & Adam Bevan: T775- where RCF cracks are formed in the centre 01 Further Development of the WLRM Damage of the railhead. Understanding the variables Parameter: Integration Report Rail Technology which affect premium rail steels performance Unit, Manchester Metropolitan University, is essential to ensuring that they are utilised August 2011 to give the greatest benefit without increasing the risk. [4] S.L. Grassie, J. Kalousek: Rail corrugation: characteristics, causes and treatments, Due to historical wear issues, LUL has more Proceedings of the Institute of Mechanical track-based lubrication than required but it is Engineers, Part F: Journal of Rail and Rapid not just an engineering challenge. A culture Transit, 207F, 57 – 68, 1993. where track inspectors expect to see large Figure 25: On board adhesion volumes of grease on the railway means Please note, some images in this article are that moving to train based solutions where management system small due their resolution. there is not such obvious visual evidence is often met with scepticism. Managing the top of rail friction is almost as important as the gauge corner with the levels of forces being generated in sub 200m radius curves.

Noise and vibration is an area which is extremely difficult to manage for LUL. This is due to the root cause often being a lack of understanding at the design phase, which is extremely difficult to solve with retrospective solutions, and the interpretation of the perceived benefits.

Optimising the wheel-rail interface on LUL is extremely difficult given the constraints which are imposed by the requirements of modern Figure 26: Pandrol Vanguard resilient track fixings

84 JOURNAL OF PROCEEDINGS TECHNICAL

Design challenges AUTHORS:

Hanno Toell for urban-railway Dieter Pichler BCE transport systems

Examples of the development of ballastless trackforms including noise and vibration mitigation for metro lines

ABSTRACT The systems are analysed with numerical INTRODUCTION models in order to be tuned to the required Inner-city metro sections are highly frequented insertion loss for optimal mitigation of impacts Rising mobility requirements and growing and they cross densely populated urban on the receiver. Different ballastless track city centres require an extensive expansion areas. Track systems to be installed have to systems have been developed for Metro of public transportation networks in order take both of these aspects into account. This Doha (Qatar) and Wiener Linien (Vienna to improve the city’s inhabitants quality of requires a high performance design resulting Public Transport System, Austria) and will be life. Due to their high capacity and their in low impact on the environment in terms of presented in this paper. effective use of energy with low impact to the ground-borne noise and vibration. Ballastless environment, railways are one of the most trackforms offer a state-of-the-art technical The system for Metro Doha includes a important transportation systems for the future. solution to fulfil both requirements. prefabricated slab track element installed on a Inner-city metro sections are highly frequented concrete blinding layer. The system has been and cross densely populated urban areas. This The structural design of ballastless trackforms developed for installation in tunnels, at grade requires transportation solutions independently has to take into account limiting factors, such and on elevated viaduct sections. from the surface level on viaduct sections or in as space availability and maximum tolerable the underground. deflections and it has to provide a holistic best Vibration sensitive areas are equipped with outcome solution for any given traffic loading, heavy or light weight mass-spring systems. Limited space conditions, limited maintenance vehicle dynamics and subgrade in order to The system for Metro Vienna is a system with intervals and the requirement for high minimise costs over the entire life-time of the booted bi-block sleepers mounted on a track availability and high performance are crucial system.In vibration sensitive areas, ballastless slab for installation in tunnel sections. The parameters to be considered in the selection trackforms can be executed as a mass-spring track slab is supported by an elastic element of the track system. Due to these reasons, system. of polyurethane (PUR), providing vibration ballastless track forms are becoming more and mitigation. more important.

Figure 1: Schematic description of the coupled train-track system. The left figure represents a heavy mass-spring system; the right picture shows the qualitative mechanical representation of the system in terms of masses, springs and dampers

85 TECHNICAL JOURNAL OF PROCEEDINGS

Such trackforms show a lot of advantages in The following aspects need to be considered: with respect to a reference structure without an regard to load carrying capability and to the additional elastic element. long term stability of the track with minimum • Consideration of long term resistance by of maintenance needs. Nevertheless one of using fatigue design principles according The comparison is normally done in terms of the most important issues of track systems to the latest analysis and EN standards a third octave band spectrum Lv2 (third octave is the noise and vibration impact of standard • Using specialist techniques such as band of vibration velocity) with respect to the systems. Especially in densely populated fatigue resistant principles in concrete structure-borne noise of a reference structure areas and centres where railway routes are design (no pre-stressing, no welding of Lv1 or by means of a mean value that depends in tunnels very close to residential buildings, the reinforcement, reduce stress peaks, on the specific frequency range. Therefore, IL

the acceptance of new railway lines is low etc.) can be expressed as: IL = Lv1 – Lv2. especially by potential neighbours. • A maintenance free design; removing the need for routine maintenance of the The determined IL also serves as a measure To reduce ground-borne noise and in particular system over the longest possible life-time to assess the damping effectivity of a track vibration impact for residents, ballastless • Robust design principles at critical superstructure compared to a reference track. track systems can be executed with optimised sections, (for instance at transition zones To characterise the effectiveness of the track elasticity (soft fasteners or mass-spring between ordinary track and bridges), vibration mitigation due to the elastic element systems) which have been developed in the based on structural dynamics which is represented by the insertion loss, last years. With such systems the emissions • Focus on interaction between structure an analytical model is developed taking into can be reduced far below the level of ballasted and substructure (e.g. between bridges account the trackform, its elastic elements and track systems. and permanent way longitudinally as well the masses and springs of the train. as laterally especially in areas of bridge STRUCTURAL DESIGN OF joints) Figure 1 shows a schematic description of BALLASTLESS TRACKFORMS • Vibration mitigation through the use of the vibrating parts of the coupled train-track soft rail fasteners system. A precise calculation of the insertion loss of this system implies solving for all The design of ballastless trackforms as part of relevant degrees of freedom (DOF) due to a an overall track system needs to accommodate VIBRATION MITIGATION WITH given excitation and evaluating the vibration the typical operating conditions of metros MASS-SPRING SYSTEMS mitigation at the tunnel bottom, being a part of and take into account all relevant interfaces the foundation. In state-of-the-art procedures (switches and crossings, viaducts, tunnels, Different construction philosophies have been for computing the insertion loss, see DIN earthworks, signalling etc). Ballastless metro developed during the last 25 years in order 45673-4, predominantly vertical modes of track systems need to be applicable to all these to provide vibration mitigation systems for vibration are observed. substructures. Typical challenges that need to ballastless track systems. All these systems be considered are: consist of a more or less heavy sprung mass In order to achieve a detailed description of the on which the rails are mounted. The bearings transmission of the vibration from the rails to • Requirement for high performance and can either be real steel springs or made of the foundation, a model that takes into account high track availability artificial or natural elastic materials. The all vibrating components of the coupled • Applicability to tunnels, bridges, troughs dynamic performance of a mass-spring system train; track system and their corresponding and ground-level structures depends very much on the material used for stiffness needs to be found. Preliminary • Limited space requirements (width, the bearings. The differences occur especially studies indicated that this can be satisfactorily construction height), in particular for due to non-linear effects of the different achieved by means of coupled mass-spring tunnel routes materials. systems if the influence of the train is reduced • Life expectancy > 50 years to a resulting unsprung mass of the wheelset • Great adjustability both in height and The mass consisting of reinforced concrete and the bogie. Such a model includes: position with a rail carrying system mounted can be • Compatibility with all established train either a chain of short elements connected • Unsprung mass of the train: assuming control and train protection systems by hinges or a jointless slab several hundred that the train wagon is mounted at a • Possibility for special equipment metres in length. In the first case a single- frequency in the area of very low Hertz, (absorber and trafficability systems, etc.) degree-of-freedom (SDOF) model seems to be the resulting unsprung and dynamically • Repair options for rail support or the total an appropriate simplification, whereas for the active mass is reduced to the mass of system within minimum time slot joint-less system, more detailed investigations wheelsets and bogie. If furthermore it is • Overall cost-effectiveness (initial on a multi-degree-of-freedom (MDOF) model regarded that the point mass leads to an investment costs and life-cycle costs) are necessary. appropriate bending line of the rails due

to their stiffness, this mass distributes The structural design must be developed in DETERMINATION OF TRACK evenly over a certain rail section. accordance with European Standards for slab INSERTION LOSS • Mass of rails and rail fastening system design including EN 16432-1 and EN 16432-2. (m ) The loading requirements of track systems rail A crucial aspect of designing mitigation • Spring (c ) in regard to the dynamic in vertical, lateral and longitudinal directions fast measures is to provide an indicative stiffness of the rail fastening system (e.g. have to be taken into account. Loading regimes specification for the resilient components and plastic pads, PUR pads, base plate, cork- in the vertical direction are usually based the mass of the different trackwork types, rubber pads etc.) on the load model LM71. Track resistance in resulting more generally in the assessment of • Vibrating mass of the sleeper or slab (e.g. the lateral direction is essential and will be the evaluation of the track insertion loss (IL). elastically supported) determined in conjunction with all required The insertion loss of the mitigating trackforms • Spring (c ) in regard to the dynamic standards. dyn is a measure for the damping due to the use of stiffness of the elastic components elastic components compared to a reference (rubber pad, resilient layer, rubber boot Special requirements arise for the application track system without additional elasticity. In etc.) of ballastless tracks in regards to safety, accordance with DIN 45673-4 the insertion • Vibrating mass of the foundation m considering ageing processes and continuous found loss is defined as the decrease in the ground (e.g. tunnel tube). maintenance of the system or parts of it. borne noise on the tunnel bottom of the test • Spring (cfound) in regard to dynamic structure, where an elastic element is inserted, stiffness of foundation and underground

86 JOURNAL OF PROCEEDINGS TECHNICAL

The modelling of the coupled train-track It is common practice to characterise mitigation system results in simplified model with 3 measures not only by the insertion loss, but,

degrees of freedom (Multi-Degree of Freedom more simply, by the natural frequency f1 of the Model – MDOF). This coupled system can be system. This value is based on a response described by a set of equations that describe amplification factor of a dynamic system and the fundamental laws of mechanics. The can be explained in a very simple way by following system of equations results: a linear single-degree-of-freedom system according to figure 2. Vibration attenuating effects occur only for frequencies starting from

f1√2. Therein describe the mass matrix, the stiffness matrix, the damping matrix and According to the characteristic natural the vector of deflections, respectively. The frequency of the system, the following components yield: classification gives an overview of commonly installed mass-spring systems:

Figure 2: Mass-spring system

In the following sections, the above explained Based on these requirements, the slab as the principles will be presented on the basis of system’s core element was adapted in regard projects taken from practical experience. to:

TRACK SYSTEM OF METRO • slab dimensions DOHA • fastening system • derailment containment • requirement for a large variety of cable Phase 1 of the Metro Doha network consists crossings of 4 metro lines with an overall track length • unrestricted fixation of power rail of approx 132 km, including underground, • improved stray current isolation elevated and at-grade sections scheduled The external force is chosen as harmonic P for opening in 2019. Within the complete excitation force: The selected rail fastening system corresponds network a derivation of Slab Track Austria to Vossloh 300 UTS. The track slab element (STA) was installed. STA is a ballastless track In certain cases this general model needs to of STA for Metro Doha is a precast concrete system designed by VCE and developed by be adapted in order to describe the problem. element in the standard dimensions of 2.1 m the construction company Porr. Originally, the This 3 MDOF model can be directly used to x 4.1 m x 0.165 m including 6 supporting point system was developed for application on high describe the vibration transmission across rows (Figure 3). On the bottom of the slab, an speed and high capacity track for the Austrian track system. elastic layer is glued to the concrete surface. Federal Railways (ÖBB). For application on The slab includes derailment containment for metros this system was modified by VCE in line If all parameters are known, the system of the entire network. The gaps between each with specific requirements. The track system equations can be solved for the displacements slab separate the slabs and compensates consists of a prefabricated concrete slab in vector and the vibration transmission and for any deformations caused by creeping, x with an elastomeric layer underneath. STA is the damping properties can be evaluated. shrinking or temperature changes. Furthermore installed on standard track (SST), switches and Therein, the vibration damping is determined they can be used for cable-crossings. Every crossings and mass-spring systems in sections by comparing the frequency dependent slab has two rectangular grouting openings requiring noise and vibration mitigation. The displacements of the foundation x with the which are tapered shaped (the width and the 3 design included light mass-spring systems deflection of the rails x . length of the opening are smaller on the bottom 1 (LMSS) supported on full surface bearing and than on the top of the slab). This tapered heavy mass-spring systems (HMSS) supported shaped grouting concrete works as an anchor on discrete single point bearings. in vertical and horizontal (shear key) direction to keep the slab in place. Main design parameters and system characteristics: Maintenance openings allow the installation of shafts/manholes in the track, which can be • Axle load 16 t necessary for maintenance purposes (e.g. for • Minimal radius of 168 m the tunnel drainage under the track). • HMSS with varying natural frequencies of Finally, the IL is determined by comparing 6.0 Hz, 8.4 Hz, 11.4 Hz the frequency dependent displacement of the The slabs are supported and fixed on a thin • LMSS with natural frequency of 11.4 Hz foundation of the reference system x with base layer of self-compacting concrete (SCC) (2,ref) • Special sections of HMSS on switches the foundation displacement of the test system that is cast after having positioned the slab and and crossings in the main station x : the rail. This allows homogeneous setting. On (3,test) Msheireb concrete hardening, the tapered joints work • Total height of the system (top of rail to as anchors to keep the slab in place vertically elastic element): 95 cm (HMSS); 75 cm and horizontally. If required, the system is (LMSS), 47 cm (SST). installed on a concrete slab that is supported on elastic elements acting as a mass-spring The project development and system system (figure ).4 The power rail is fixed with configuration took into account the pre-installed dowels drilled on site. The slab specifications and configurations defined by includes defined areas with the possibility for Qatar Rail. drilling.

87 TECHNICAL JOURNAL OF PROCEEDINGS

CONSTRUCTION SEQUENCE OF MSS

In order to enable the installation of discrete single point bearings underneath the grouting concrete, various solutions were investigated. The first possibility consisted of installing the bearings as a first step and mounting prefabricated concrete elements as a lost formwork for the grouting concrete as a second step. This method could not be applied to Metro Doha due to practical reasons (limited available space for handling prefabricated concrete elements and slow construction progress). Another solution included the installation of filling material in between the bearings enabling a plane surface ready for the concrete grouting on top of it. This solution was not able to fulfil the vibration mitigation requirements and the requirements for replacement of the bearings. As a consequence, VCE followed the more innovative concept of installing the bearings after the completion of the grouting concrete. A separation layer was installed directly on the infill concrete. The grouting concrete was cast directly on the first-stage infill concrete. After the curing of the concrete, the entire HMSS was lifted with hydraulic jacks placed in the maintenance opening and the bearings were inserted. To accommodate the jacks, special design adaptations were required (cavities for jacks and locally strengthened reinforcement, figure ).5 The application of this method was the only one able to fulfil the stringent criteria for replacement of the bearings.

LATERAL RETAINING

In the case of standard track, the lateral retaining occurs directly through the monolithic concrete block of the infill concrete in the Figure 3: Cross section and top view of slab track tapered joints. In the case of mass-spring

Figure 4: Cross sections of standard track (left), LMSS (centre), and HMSS (right)

88 JOURNAL OF PROCEEDINGS TECHNICAL

Figure 6: Lateral HMSS bearing

ORIGINAL TRACK SYSTEM ‘ALTER WIENER OBERBAU’ - Figure 5: Cross sections of lifted HMSS with hydraulic jacks placed in the 1969 maintenance opening The ‘Alter Wiener Oberbau is a ballastless track system with plastic sleepers mounted in rubber boots. The boots are fixed into a concrete element loaded on a mat of a sealed mineral wool panel (figure 7).

• Total height of the system (top of rail to elastic element) is 53 cm • The natural frequency of system is 20-23 Hz.

At the beginning of the year 2000, the experience of the last 25 years in operation has shown some disadvantages of this system. The main disadvantages are problems with the long-time behaviour of the elastic layer between the track slab and the foundation Figure 7: Schematic cross section of Wiener Oberbau 1969 leading to problems with the track stability, fatigue problems with the artificial sleepers and the barely walkable open drainage ditch in the systems, the problem is more complex. In order to fulfil this criterion, the transition track axis. Therefore, Vienna Public Transport The lateral forces acting on the LMSS are length was determined at 25.2 m, System installed a working group of experts for supported by the shear resistance of the (corresponding to 6 slabs of 4.1 m including noise and vibration, railway engineering and elastic mat that is placed in a trapezoidal 6 joints of 10 cm). The bearings for transition maintenance to develop a new ballastless track shape. As this system has a very stiff mat, the zones have the same height as the standard system, named ‘Neuer Wiener Oberbau’. VCE lateral restraint of the elastic mat is sufficient bearings. was the leading partner in this group. to withstand the forces and reduce the lateral The stiffness of the elastic material is movement to a minimum. In the case of the IMPROVED TRACK SYSTEM HMSS, the lateral movement of the mass- subdivided into 3 parts over the length of the spring system depends on the shear capacity transition zone. ‘NEUER WIENER OBERBAU’ - of the discrete single point bearings. The 2003 dynamic assessment of the point bearings The difference of the bearing stiffness between specified a requirement of lateral bearings in each consecutive bearing arrangement is Since 2003, a solution with twin-block sleepers a distance of 42m. The design foresees two about twice the stiffness of the preceding zone. has been installed. The Neuer Wiener Oberbau elastic bearing blocks (one on each side of the is a ballastless track system with bi-block HMSS) with a static bearing stiffness of TRACK SYSTEM FOR METRO sleepers mounted in rubber boots embedded c = 150000N/mm coated by a Teflon layer in a continuous floating concrete track slab stat VIENNA (PTFE) in order to allow the bearings to slide (figure ).8 Instead of mineral wool panels, polyurethane is used. (figure ).6 Since the first installation of the basic metro network in Vienna in 1969, underground • Total height of the system (top of rail to TRANSITIONS sections of the network were equipped with elastic element) is 53 cm ballastless track. This system, well known • The natural frequency of system is 18.5 At the beginning and at the end of each MSS, under the name “Wiener Oberbau” was Hz. a transition zone was provided, to ensure a developed more than 45 years ago. In addition

gradual stiffness change of the track. The to its low noise and low vibration features this The constant development and increase length of the transition was determined based track system has other significant advantages, in train services necessitated once again on the maximum travel speed of 80 kph and such as replacement of all components and an improvement of the track system. In the the assumption that for passenger comfort the easily cleanable drainage ditch in track axis. year 2006, a new train type was introduced, track stiffness should not change for a minimal The system was continuously adapted and enabling shorter service intervals and higher travel time of 1 s: improved. vibration emissions due to slightly increased axle loads. Furthermore, in the 2010, the city of Vienna introduced a 24 hour metro service at weekends. As a result, more stringent

89 TECHNICAL JOURNAL OF PROCEEDINGS

vibration limits during night-time have to be applied within the network. Due to both of these aspects, the network operator decided to develop a ballastless track-system with improved mitigation behaviour. This system will be applied to all tunnel sections of the future network expansion. For example, for the new U5 line currently in the tender phase. VCE developed a catalogue of measures. This catalogue assessed measures with widened tunnel profiles, a variation of the elastic components by maintaining the dimensions of mass and concrete of the existing ‘Neuer Wiener Oberbau’ system at the same time and finally, a variation of the dimensions of the Figure 8: Schematic cross section of Neuer Wiener Oberbau 2003 mass-spring system. In a cost-performance evaluation taking into account design, construction and service phase over the entire life-cycle, the decision was made to further improve the system ‘Neuer Wiener Oberbau’ with increased concrete mass and modified elastic elements.

CURRENT SYSTEM ‚WIENER OBERBAU - 2018

The system is a ballastless track system with bi-block sleepers mounted in rubber boots. The boots are fixed in a concrete block loaded on a polyurethane mat, (see figure ).9

• Total height of the system (top of rail to elastic element): 80 cm • Natural frequency of system: 12.8 Hz Figure 9: Schematic cross section of Neuer Wiener Oberbau 2018 • Axle Load: 11.5 t • Special sections of HMSS in sections with In specific situations damages occurred due replacement at regular intervals. In order to switches and crossings to bad welding execution. Measurements reduce maintenance costs, observations for evidenced, that these damages occurred due improvement of the current system were made. The fastening system corresponds to the to irregular deformations of the sleeper in In the design phase for the new fastening KPO clamp fastening system. The bi-block relation to the slab track. The deformations systems, the following aspects needed to be sleepers of pre-stressed concrete are coated induced very high vibrations in the anchoring, considered: with an elastic component (polyurethane or a material fatigue and a loosening of the bolts. rubber). The power rail is fixed directly on Due to this reason, the Wiener Oberbau 2018 • Tolerable deflections under static load the track slab. Horizontal and vertical elastic includes an improved fixation concept for • Rail head tilting bearing elements are custom-fitted materials of the power rail. The vibrations on the slab are • Rail guidance in the ripped base plate polyurethane (PUR) developed in collaboration lower compared to those on the sleeper. For • Selection of fastening system based on with the manufacturer Getzner. For dewatering this reason, the anchoring is now located on durability aspects and revision each 22.4 m long section includes the slab track itself. The system consists of a • Transition to Wiener Oberbau 2018 a maintenance opening of 40 x 40 cm in the monolithic precast concrete mounting socket • Comparable vibration mitigation centre. The surface water drains off through with an elastic layer pad on top. The third rail behaviour to Wiener Oberbau 2018 this opening and is collected in a drain channel bracket is mounted on top of the socket (figure underneath the track system. 11). The socket is positioned and aligned prior The principle of the newly developed system to the grouting of the concrete. Three dowels is the change in location of the elastic pad. JOINTS AND LATERAL are aligned prior to the grouting. After curing of It has been moved from underneath the the concrete, the dowels are connected to the ripped base plate and installed in between RETAINING slab track, mounting socket and bracket. the base plate and the bottom of rail. This results in a reduction of vibrations in the For ease of construction, the track system is DIRECT FASTENING SYSTEM IN sleeper bolts. Due to construction reasons, manufactured in sections of 22.4m. The joints SWITCHES & CROSSING AREAS the new system requires fastening clamps. are connected with shear force dowels in order The new system is currently applied to a test to link the sections to a continuous floating section in the network and is being assessed The installation of bi-block sleepers in switch concrete track slab (figure 10). The dowels with different measurement campaigns areas is not effective due to many different are an approved system for dynamic loading (durability, deflections, vibrational behaviour geometric restrictions and limited space conditions. The lateral retaining results directly etc.). A life-cycle assessment resulted in conditions at the intersection of the rails. from the shoulder of the sub-concrete. the demonstration of a better cost-benefit For this reason, switch & crossing areas of the ratio of the new system in comparison to the ‘Wiener Oberbau’ are installed as mass-spring FIXATION OF POWER RAIL previous one. It is intended to install the newly systems with soft and highly elastic fastenings. developed fastening system on the new U5 Figure 12 shows the solution executed in the The original power rail fixation of the ‘Wiener line. traditional track system since 2003. Regular Oberbau’ included a direct fixation on the network inspections revealed damage due mounted sleepers. to fatigue of the sleepers bolt, requiring

90 JOURNAL OF PROCEEDINGS TECHNICAL

CONCLUSIONS

Ballastless trackforms offer a state-of the art technical solution for urban transportation systems. The increased noise and vibration impact of standard systems in densely populated areas can be addressed with the installation of vibration mitigation systems such as mass-spring systems. There is a vast quantity of ballastless track systems installed over the entire globe, each having benefits but also disadvantages. Designing an effective track system is a task requiring vast experience. Nonetheless, constant monitoring of the performance of the track system over the service period is essential in order to continuously improve the system. A good design of ballastless trackforms needs to accommodate the disadvantages by means of cooperation between constructor, operator, system supplier and external experts. On such a basis an optimal track system for the entire life-cycle with low impact to the environment is possible.

REFERENCES

Figure 10: Shear force dowel in joints EN 16432-1 Railway applications - Ballastless track systems - Part 1: General requirements; German version EN 16432-1: September 2017

EN 16432-2 Railway applications - Ballastless track systems - Part 2: System design, subsystems and components; German version EN 16432-2: October 2017

DIN SPEC 45673-3 Mechanical vibration - Resilient elements used in railway tracks - Part 3: Experimental evaluation of insertion loss of mounted track systems (in a test rig and in situ): August 2014

DIN 45673-4 Mechanical vibration - Resilient elements used in railway tracks - Part 4: Analytical evaluation of insertion loss of mounted track systems: July 2008

Buda, R. 1996. Elasticity in Modern Figure 11: Power rail fixation Superstructures – system design aspects and typical components. Getzner Werkstoffe Ges.m.b.H., Austria

Clough, R.W. & Penzien, J. 1993. Dynamics of Structures. Second International Edition, McGraw-Hill.

Pichler, D. 1997. A new Vibration Attenuating Trackform for Railway Tunnels – Römerbergtunnel. ÖIAZ 142 Jg., No. 4, p. 306.

Pichler, D. et al. 1997. Entwicklung eines neuartigen Masse-Feder-Systems zur Vibrationsverminderung bei Eisenbahntunnels. Bauingenieur 72 p. 515-521.

Figure 12: Schematic layout of highly elastic fastening system in switches & crossing locations. Traditional system 2003 (left) and improved system 2018 (right)

91 TECHNICAL JOURNAL OF PROCEEDINGS

Milano: A mature AUTHOR:

Dott. Arch. Andrea Bruschi urban rail network Milano Metro - Mobility Planning and Feasibility Studies

that needs to Dott. Ing. Sergio Viganò Milano Metro - Infrastructures Design expand outside and Urban Redesign Unit Responsible the city

The purpose of this paper is to provide an to the good standards achieved by northern, Milan has a privileged location as a natural overview of the rail guided mass transit central, western and more recently also other gateway between Italy and Europe, a node public transport system in Milan and its Mediterranean countries such as Spain. from which departs six of the main segments developments, backbone of metro area Athens itself has a much better mobility asset of the European network. This is evident mobility and keystone of City’s current and a lower motorisation index than Rome. since the beginning of Milan’s more than renaissance significantly based on sustainable bimillenary history as its name itself means mobility revolution, highlighting some MILAN METROPOLITAN “In the middle of the lands”. This has given a particular solutions adopted in the transport MOBILITY CONTEST strong infrastructural background to the city, infrastructures to cope with the densely built while its dynamic, innovative and international urban fabric. attitude has always boosted more rational Luckily, there’s a remarkable exception: Milan. technological solutions. Italy’s economic capital, most international and ITALY’S NATIONAL MOBILITY dynamic city, largest metro area and second That’s why today Milan has achieved excellent CONTEST municipality has always been closer to best results in public transport and sustainable European standards than to the Italian average mobility, which though this is an exception in Italy is unfortunately lagging behind in urban in many fields, and in mobility it’s self-evident. Italy it is a very good case in the EU. Milan and metropolitan public transport. In cities Even more remarkably, this has recently City boasts a very ‘sustainable’ modal split as and larger metro areas, private cars hold a far increased significantly. public transport share is more than 57% with larger share in mobility, so that the modal split private cars barely reaching 30%. Bikes count is definitively unbalanced in favor of cars. As a Today Milan is a large metro area of 5,25 for approximately 6% which means that almost nation, Italy is the world’s 4th country for cars million inhabitants; by far Italy’s largest metro ⅔ of the cake is based on green mobility. per capita with 68 for every 100 inhabitants, area and among the 4 largest areas in the EU. Motorbikes count for 7%. This modal split dates overtaken only by the US, New Zealand and It is only overtaken by London and Paris. It back to 2013 when the last official statistics Australia, which are less dense (33, 18 and produces 1/7th of Italy’s GDP, being its richest were available. However, according to other 3,3 inhabit./km² while Italy stands at more than area by far. Milan’s Municipality, Italy’s second indicators, partial polls and surveys, the actual 200). Italy overtakes Canada in 5th place with by population, has a 1,4 million inhabitant public transport share should be closer to 60% 66 cars/100 inhabitants, although Canada is population over 182 km², generating a high and total green modes in excess of ⅔. more than 33 times larger and more than 60 average density of about 7.700 inhabit./km². times less dense. After a classic post-industrial demographic It is important to note the recent boost in loss started in the mid ‘70s and culminated sustainable mobility. As previously stated, Rome, Italy’s capital, larger municipality and in 2011 census at the minimum of 1,2 million Milan has always been an exception in Italy second metro area, is Europe’s most motorised inhabitants, Milan Municipality population regarding public transport, having a greater city with a bewildering 72 cars for every 100 started increasing by 25.000 new inhabitants share than private cars for several decades. inhabitants; basically more cars than people per year. This increase was mostly due to According to official statistics released in able to drive. Public transport share in Rome immigration from Italy, EU and other parts 2005, public transport approached 51%. For doesn’t go much further than 20% and bike of the world and consisted typically of 18-45 several years before, it was stable between share is so low to be approximated to zero. year old active people. Milan is home to Italy’s 45 and 50%. From 2005 to 2013, it gained 6 And it’s not even the worst case: Palermo, largest concentration of banks, universities, percentage points, almost one per year. Cars Sicily’s capital with some 800.000 inhabitants services, media headquarters, enterprises per capita were 64 per every 100 inhabitants in the metro area, stands at only 9%. A 10-25% and multinational corporations, the stock just 10 years ago, less than national average public transport share is the average in most exchange, Europe’s largest fair and the world’s but still a lot. Nowadays they have decreased of larger cities including Naples, Italy’s 3rd 2nd highest number of consulates after New to just 51, in line with the EU average and way municipality and metro area as well as Italy’s York City. It is also Italy’s 4th City of artistic below the Italian average. It is still more than densest metropolis, Florence. In medium-sized heritage, (after Rome, Venice and Florence the average in the large metro areas of the EU, cities, public transport share is often lower than and therefore among world firsts) according 42, but all signs indicate that such a target will 10%. to UNESCO and 2nd for tourism after Rome, be achievable shortly. overtaking the capital in 2015 due to EXPO, These worrying statistics make public transport plus being well known as a world fashion and and sustainable mobility one of the most design capital. critical aspects of Italy, especially compared

92 JOURNAL OF PROCEEDINGS TECHNICAL

ATM, the public transport operator, totaled about 700 million passengers per year in 2012-2014, gradually growing from 695 to 710. Then, in 2015, the year of EXPO which lasted six months from May 1st to October 31st, passengers peaked at 736 million. But what is very interesting and significant is that after an obvious, expected decrease to 728 million in 2016 (EXPO had 22,2 million visitors), in the year 2017 ATM passengers unexpectedly peaked again at 750 million, a new historical record overtaking even the EXPO year. This has been the best proof that the new public transport infrastructures and policies applied to its network, have led to a solid, long- term enduring and positive change towards sustainable mobility.

Furthermore, a 2018 McKinsey study on public transport in world metro areas rated Milan in the world’s top ten, based on availability, efficiency, comfort, costs and sustainability. Not a surprise since Milan has been Italy’s leader in public transport for decades, but getting into the world top ten is an epochal fact. MM played an important role in advising Milan’s administration in the development of mass public transport network, ensuring all the sustainable mobility policies including accessibility to mass transit infrastructures and car disincentives were affordable.

URBAN DEVELOPMENTS

Milan’s renaissance has been due in the main to its public transport, but the development of real estate has also contributed. Few world cities are currently able to boast, in both absolute and relative terms, the quality of urban spaces just developed, under development or soon to be developed as is Figure 1: Modal split evolution in Milan and metro area. Green is public happening in Milan. In Italy no city is a match, transport, red cars, yellow motorbikes and blue bikes. The left column is in quantity and quality, but also on a European scale, Milan is actually demonstrating the 2005, the right one 2013. Top row is city - metro area trips, middle row greatest examples of urban requalification city trips and bottom row total trips. (Source: PUMS, AMAT) and refurbishment on the Continent, especially based on functional changes For the first time in history, and in spite of passed the majority 50% share at metropolitan and developments. Also on a world scale, active people immigration based demographic level. The problems are not completely the “share” of the City “re-invented” and the growth, the number of new driving licenses solved. The metropolitan modal split includes impacts of such a massive phenomenon on among 18-21 youngsters dropped by 50%, both inner city, the Milan Municipality and its society is definitively not a common occurrence something that has never happened before metropolitan ring, but when analysing the latter compared to the quickly growing dynamic in Italy and which is alien to its car-addicted in isolation, cars still have the largest share in financial centres and capitals of south-east culture. As NYT stated few years ago, modal split; 58% in 2013 but still less than 62% Asia. “Millennials don’t drive”. This is also about to in 2005. The current percentage is probably happen in Milan. not more than 55%. However, the forthcoming As a major transportation node Milan offers challenge for Milan public transport is to broad accessibility to urban polarities. Milan In the metro area mobility results can’t be as expand more effectively the public transport brings together 12 main, huge and strategical good as in the inner city, but even so in this alternatives to its metro area. urban refurbishment areas, along with many area the modal split is good enough. Public more minor cases: transport has the largest share with 48%, Ultimately, public transport and sustainable which combined with the bike at 3% makes mobility as a whole set of policies have 1. P.ta Nuova, 340.000 m², almost green modes the majority with 51%; private developed a lot in recent years, exploiting completed and integrating Milan’s main cars are at 43%, motorbikes are at 6% making the historical occasion of EXPO2015 World CBD; 49%. In these cases progress is evident as in Exhibition which took place in Milan in 2008. 2. City Life, 366.000 m², almost completed 2005 cars were still getting the larger share Since then, important investments have been other CBD, which has replaced former with 49%, getting to a majority of 54% for made in the city, especially in mass mobility Fiera district; private motorised vehicles when combined with infrastructures, reinforcing an already strong 3. Milanosesto, 1.500.000 m², largest EU motorbikes. This data refers to 2013. Therefore network and boosting public transport share redevlopment area, under planning; it’s probable that by now public transport by and trips. replacing steel factory Falck with a health itself, without including bikes, has already complex;

93 TECHNICAL JOURNAL OF PROCEEDINGS

Figure 2: Main urban redevelopment areas in Milan and metro-rail mass transit network (Source: Polytechnic of Milan, MM)

4. Westfield Milan, 610.000 m², under these remarkable developments are based on and a functional mix of functions – high quality construction; future largest mall in Europe a strict, reciprocal correspondence between residential unities, a new park, museums and replacing former freight customs area; the generational need and the public mobility public services buildings, all of them centered 5. MIND, Milan Innovation District, offer according to today’s TOD (Transit on a central square framed by three archistar 1.200.000 m²; under planning/ Oriented Developments) concept. Milan’s designed iconic skyscrapers. The square in construction, on former EXPO2015 world high density challenge forced the focus on between the skyscrapers is the hub of the exhibit site; underground works to create infrastructure entire area, which has wide 4 levels below for 6. Farini railyard, 615.114 m², to be planned nodes and mass mobility access infrastructure. underground basements and parking, also on dismissed area belonging to so called Mass mobility underground is like roots for deployed around the central square, whose Railyard Agreement; the amazing high-rise developments above architecturally generating function is evident. 7. Romana railyard, 212.207 m², to be ground. More specifically, it is possible to refer planned on dismissed area belonging to to the trilateral agreement in the definition Tree Towers (Tre Torri) refers to both a square so called Railyard Agreement; of the underground asset of Porta Nuova and a metro station. Referring to the three 8. S. Cristoforo railyard, 171.683 m², to be due to M5 works, planning P.ta Nuova CBD, iconic skyscrapers (from Volume II of the planned on dismissed area belonging to an almost totally pedestrian and green area famous JRR Tolkien novel Lord of the Rings). so called Railyard Agreement; in between skyscrapers and above huge Tre Torri square has two levels corresponding 9. P.ta Genova railyard, 102.291 m², to be underground parking lots. Today at Garibaldi, to the skyscraper’s atrium and upper planned on dismissed area belonging to P.ta Nuova Location, underground railway basement. The lower basement is merged so called Railyard Agreement; link, M2 metro line and the new M5 metro directly with Tre Torri station mezzanine, 10. Greco railyard, 72.176 m², to be planned line, the interchanges can carry up to 134.840 according to the idea of creating an open on dismissed area belonging to so called pph underground and up to 169.080 pph by space logic between mass transit infrastructure Railyard Agreement; 2025 due to M5 and underground railway link and common public spaces in between 11. Lambrate railyard, 70.716 m², to be improvements. business towers. In order to merge the building planned on dismissed area belonging to sites and to provide a wide, underground so called Railyard Agreement; Including Garibaldi railway station (served also space to fit the M5 line with shunting tracks, a 12. Rogoredo railyard, 21.079 m², to be by regional, commuter, long haul, HSR and massive 400 m long and 20-30 meters wide planned on dismissed area belonging to MXPexp trains) and surface transportation room has been placed between underground so called Railyard Agreement. such as trams and buses, the node’s capacity lots, sharing their side walls. Like the open already peaks up to about 160-170.000 pph space logic above, a wall sharing logic has All of these areas total more than 5,25 million today and will overtake 200.000 by 2025 been implemented below and building sites square metres, will host strategic urban confirming itself as Italy’s most accessible have been partially merged. functions with massive recall and are based on area by rail and from the underground. This mass infrastructural developments. exceptional accessibility perfectly matches with Private operators has been incentivised to Milan’s and indeed Italy’s tallest skyscrapers. cooperate in the creation of a major mass Unlike the several massive and disorganised The main vision of CityLife CBD driving its transit infrastructure building. The massive real estate speculations which characterised masterplan has been a completely pedestrian underground area containing the station’s Italian history in the ‘60s, ‘70s and ‘80s, all of and green area with no cars and internal roads “box”. This was completed after two TBMs

94 JOURNAL OF PROCEEDINGS TECHNICAL

excavated two single track galleries. Tre Torri advantage could be provided by the possibility In both the Milanosesto and MIND cases has been one of the most remarkable cases of combining the building sites M4, Porta planning will be based on existing metro-rail in which a private operator completed in Est railway station and LIN revdevelopment infrastructures, properly optimised. The same advance part of the civil works belonging to masterplan. Using a TBM greatly reduces approach is planned for the forthcoming rail metro infrastructure. Furthermore, the entire impacts on the surface as excavation is made yards, involving also in this case new stations masterplan has focussed on the leading role of substantially from underground. But TBMs and a new metro line “M6”. metro station, merging its mezzanine with two need wide open spaces – up to 12-15.000 m² level central square, as well as underground - to be assembled, put in place and fed and an MM played a leading role in the public-private basements which have been merged with a additional space, up to 2.000 m², to recover its agreements which formed the basis of such a central area useful for operational aspects. digging front. This is not an obstructing impact successful integration and has planned most when a whole line is under construction, but of the mass transit infrastructures including The Westfield Milan case has completed the on a single extension of about 2,5 km long, rail, metro and road accessibility to EXPO2015 mass transit accessibility framework in the the impact is more evident, even though no and its site, future MIND’s one, has been eastern metropolitan area. A new HSR gate intermediate stations are foreseen, which is one of three vertexes of P.ta Nuova trilateral station – Porta Est (East Gate) – is foreseen one of the options in this case. agreement together with Milan’s Municipality on the Milan – Venice line, adjoining the and Hines Real Estate, planned M5 line and Westfield area. Between this area and City When construction of new infrastructure is not specifically the Tre Torri station construction Airport LIN, the artificial pond named Idroscalo planned in isolation, but together with others in CityLife District, set the East gate feasibility (formerly the hydroplanes runaway) stretches in a framework plan, it’s easy to coordinate station and cooperated as consultant in for more than 2 km north-south, being one of different building sites. In this case, on the two the Rail Yard Agreement between Milan’s largest urban ponds in Europe. Areas around sides of extension, we have two other major Municipality and Italian Railways. its coasts are mostly green, and therefore it building sites, Porta Est station one, and LIN wouldn’t be too difficult to link LIN and Porta requalification masterplan. An HSR station and METRO NETWORK Est throughout them using urban surface an airport, whose building sites can be merged systems such as rapid bus, monorail or even with starting and ending points related to the If all the described have sustainable mobility cable cars, as in fact has been done. But use of TBMs, determining a relevant scale- successes and urban renaissance have the one of the goals of the feasibility study was economy. mass public transport network as a backbone, the preservation of the environment, around the mass transit network has a backbone like which is the added value for re-launching the This case is very significant: TBM technology the metro one. Milan metro network today Idroscalo as a wide recreational area. is able to optimise excavations in terms of consists of 4 lines, over 101 km in length and time and cost and reduce the impact too, with 113 stations. This means that it is by As a result M4, which is fully underground but clever large scale planning has been a far Italy’s largest network, with an extension and already under construction, is the option decisive choice to achieve the positive scale comparable to all other six networks (Rome, which minimises the impact overground and effect needed to coordinate and combine the Naples, Turin, Genoa, Brescia and Catania) is why it has been valued. The Metro option necessary excavation from the surface with combined, EU 7th out of 43 by length, entire will use a TBM; in this case the TBM would other civil works. European Continent’s 7th out of 52 by stations be 9,1 m in diameter and able to dig a double number and in the world’s top 30 out of more track single gallery from Linate to Porta than 200 networks. Est / Westfield. In this case a substantial

Figure 3: Top: CityLife District and first studies of M5 station “Tre Torri” insertion; right: infrastructural node Garibaldi and P.ta Nuova CBD today, below: future Westfield Milan rendering and M4 extension to adjoining HSR gate station (Source: MM)

95 TECHNICAL JOURNAL OF PROCEEDINGS

Figure 4: Clockwise from top left: M1, M3, M2 and M5 (Source: MM, ATM)

Figure 5: Sample construction sections. Top left: single track TBM gallery (M4), top right: overlapping naturally excavated single track galleries (M3), below: mixed TBM and cut&cover excavated station, to be noticed in the latter larger diameter single tracks TBM excavated galleries hosting platforms too (M4) (Source: MM)

96 JOURNAL OF PROCEEDINGS TECHNICAL

In addition, it is expanding rapidly with the 5th The recent speed in growth of the metro In addition, within the municipal borders, there line, the M4 (existing ones are M1, M2, M3 and network is unusual for a western country and is one station every 1,94 km² and 14.894 M5), is under construction. The M1 extension is a consolidated economy, being more similar inhabitants, one station for less than 2km² almost completed and many other extensions to the “south-east Asian” booming trend. The and 15.000 inhabitants and equipment and are being planned. In 2022 the metro network Metro network grew by +28% in only five years coverage among the world’s highest and higher will consist of 5 lines, 118 km in length and between 2010 and 2015 and will grow by 50% than London. In addition, 19 stations serve 136 stations becoming both the 5th largest on in just 12 years between 2010 and 2022. the metro area. Urban coverage was just ⅓ in the European Continent by stations and the 2010, it’s as said ½ today and will be about ¾ EU’s 5th largest in length and stations, as by The Milan metro network opened on November in 2025. 2022 London won’t be in the EU. Including all 1st 1964 and celebrated its first 50 years four planned extensions, Milan’s metro network years ago, just one year later than London, the The metro network carries about 2,2 million should consist of 5 lines, 135 km in length and Mother of all Metros, who celebrated its 150th passengers per day; the busiest sections peak 151 stations in 2025, being therefore in the top birthday. Today, the existing network provides at 37.500 pphpd. Also in this case, passengers 25 of some 250 world networks existing by that 50% coverage of the city urban area. are quickly growing: according to ATM 2016- time. 2017 data, M1 passengers increased by +2,4%, M2 by +2,9%, M3 by +3,4% and new M5 line by a remarkable +11,1%.

Operating metro lines are:

• M1, red, 27 km long with 38 stations • M2, green, 40,4 km long with 35 stations • M3, yellow, 16,6 km long with 21 stations • M5, lilac, 12,9 km long with 19 station

There are also 4,4 km of inter-line links.

Under construction are:

• M4 line, blue, 15,2 km long with 21 stations • M1 red line northern extension, 1,9 km and 2 stations

Speaking about systems, all of them use 1.435 mm standard railway gauge, M1, M2 and M3 have 110 m platforms and traditional 6 cars car trains about 105 m long and carrying 1.200-1.250 passengers at 6pax/m² (according to the model), whilst the new M5 and under construction M4 are lighter and automated driverless systems, with a 50m standard for Figure 6: Passante’s Porta Venezia station, mezzanine level trains and platforms, carrying 536 pax per (Source: MM) train on M5 and 600 on M4, due to the reduced

Figure 7: Passante’s Porta Venezia station, axonometric cross section, to be noticed cellular arch structure and suspended mezzanine (Source: MM)

97 TECHNICAL JOURNAL OF PROCEEDINGS

number of seats. M1 has a power supply along 3rd and 4th rail, M2 and M3 power is supplied from overhead pantographs, M4 and M5 power is supplied by the 3rd rail.

Currently maximum frequency is 120” on the central and busiest segments of M1 and M2. Due to a signaling improvement, M3 has a 180” maximum like M5, which in spite of automation is able to guarantee a 90”, is still lacking a real depot, to be built with forthcoming extension . M4 is planned for a 90” frequency too and the depot will be completed soon after opening. Consequently, maximum capacity is 37.500 Figure 8: Milan’s high capacity tramways (Source: MM) pphpd on M1 and M2, 25.000 pphpd on M3, 10.720 pphpd on M5 (to be upgraded to 21.440 once the depot is available) and there will soon be 24.000 pphpd on M4 once completed.

Average speed is between 28 and 36 km/h, with a top speed of 85 km/h. Regarding metro construction, here are the basic facts.

M1, entirely in tunnel, made use of some relatively wide streets radiating from the city centre and in past decades, thus it could be built mostly with the cut-and-cover solution. However, in order to limit the disruption of the road traffic of the most sensitive streets, the “cut&cover” variant was introduced.

M2, which connects the main railway stations of Milano, opened in stages from 1969, needed to run through narrow streets, or even underneath many buildings, thus bored tunnels were required. Figure 9: Milan’s historic “Carrelli” tram, belonging to the ‘20s and still operating (Source: MM) In a section of M2 line, as well as for an entire part of M3 (opened from 1990) through the city centre, a special solution was adopted, with the two tracks one above the other one, in order to stay within the public surface as much as possible. As a consequence, the platforms of the stations are on different levels.

Line M5 has been the first whose galleries were almost entirely excavated by TBM. Both single tunnel for double track and twin single track tunnels typologies were utilised, due to differently sized TBMs. The first section of line 5 opened in 2013, it was extended to San Siro stadium in conjunction with Expo 2015 event. It is the first driverless metro in Milano, and is based on the Italian technology firstly used for the Copenhagen metro, but with longer trains (50 m). One of the main features of line 5 is to connect the most important urban redevelopment areas of the city, as in the case of Garibaldi-Repubblica area. In the CityLife area, developed after the fairground moved away, the metro features the station “Tre Torri” underneath the three skyscrapers distinguishing this new urban pole.

M4, under construction, will cross the entire city area, from the west (San Cristoforo railway station) to the east (Linate airport), a 15 km route with 21 stations. The first section will open in 2021, with completion anticipated by the end of 2022. This new line Figure 10: Technological tunnel built in Cinisello (Milan’s Metro Area) to will be driverless, with 47 trains similar to host moved underground utilities due to tramway construction the line 5 ones, but adopting an enhanced (Source: MM)

98 JOURNAL OF PROCEEDINGS TECHNICAL

CBTC automation technology, permitting, MM was responsible for the entire planning Clockwise; from north Gotthard – Central theoretically, 75” headway, even if 90” will be of the Milan metro network, advising the Europe, Venice – East Europe, Bologna – the operated maximum. Municipality on the concept, setting all Florence – Rome – Naples (Italian Peninsula), feasibility studies, preliminary plans, definitive Genoa – Mediterranean Sea, Turin – France, The entire line is underground, within two projects and, in most cases, being the Simplon – Western Europe. In addition single-track tunnels, bored by means of TBMs. construction manager too, with the exception several regional and local lines, including The standard internal diameter of the tunnels to of the M5 project financing case. However, MM FNM, Ferrovie Nord Milano (Northern Milan accommodate each track is 6,70 m. In the city provided high surveillance over building sites. Railways), Italy’s main network after the centre the line features deep stations located national one, go to Milan. in streets of Roman and medieval origins, and SUBURBAN RAIL NETWORK with the water table close to the surface. In this This remarkable railway network has been section the tunnels have an internal diameter If the metro network is the backbone of city underexploited for decades and scarcely of 9,15 m, in order to also accommodate the mobility, most of the larger metro area relies on used for suburban and metropolitan services. platforms of the stations, to minimise the suburban railways. Milan is Italy’s larger and The key idea and turning point to provide impact on the ground and to the adjacent busiest railway node, from which depart six key the metropolitan area with public transport buildings. routes into the European main network. has been to create a mass-suburban service gathering together most of railways lines in a single axis crossing Milan along a northwest- southeast axis, following the successful examples of central European Schnell Bahn and Paris RER.

Therefore, the central, basic infrastructure supporting the whole new system is the tunnel hosting the underground railway link called passante (literally ‘passing by’, ‘going through’). This mostly underground massive infrastructure, the largest metropolitan one ever built in Italy, is 16,5 km long, including the 10,5 km urban tunnel, has 10 stations with 250 m platforms, can host 8 double-deck coaches trains and its signaling guarantees up to 225” (3’¾) peak headway and therefore up to 26.000 pphpd capacity, even if currently peak frequency is 300” (5’) for a 19.200 pphpd system capacity. In addition to the passante, the suburban “S” lines are also running headed tracks and a beltway path.

Currently the S-lines network consists of 12 lines serving 405 km and 125 stations of which 21 are within the Municipality of Milan City. In 2025 there is expected to be 17 lines serving 470 km and 138 stations, but also an increase in the service on existing ones; e.g. the passante will increase its peak frequency Figure 10: Technological tunnel built in Cinisello (Milan’s Metro Area) to to maximum admitted, therefore, even if the length increase will be +17% and stations one host moved underground utilities due to tramway construction just +10% the service will grow about +40% as (Source: MM) the number of lines increase.

Figure 11: MM planned links to MXP intercontinental airport (Terminal 1), left, and LIN international airport, right. In first case arrow indicates the railway trench containing new rail line headed to MXP_T1, in the second case blue dashed line indicates M4 line and blue rectangle station and terminus area, currently under completion. (Source: Google/MM)

99 TECHNICAL JOURNAL OF PROCEEDINGS

Stations were interesting to build, due to their Milan’s trams are mostly mono-directional, with As has been stated, public transport has size and depth; a passante station has a the exception of the extra urban tramway to good coverage, is accessible and is running volume some 5 times larger than a metro one, Limbiate, but ATM, the tram network operator, within Milan’s municipality city limits. The main and is usually deeper. Most of the excavations is about to introduce a new generation of bi- challenge is to extend as much as possible have been completed from underground, in directional trams, making the urban terminals these characteristics in the metro area. many instances freezing the ground to prevent easier to organise. flooding while making tunnels and stations This goal has to be achieved by a proper study waterproof, as Milan has a high and growing Today Milan’s tram network is an extensive of the options, the ability to foresee via CBA aquafer. The most impressive station is and used one, but it lacks average speed, which is the proper route and also the proper “Venezia”, partly built underneath an existing this being 10-15 km/h on urban segments, system to serve a specific area, favoring a skyscraper by the technique of the so called including the new high capacity lines, unlike multi-modal approach to the solution. “cellular arch”. the rest of the EU where modern tramways easily exceed 20 km/h as an average speed. PUMS contains all the main development MM studied, planned, projected and managed This lower average speed isn’t due to planning of the public transport network. In some construction of the passante and cooperated or technical limits, but due to cultural ones, instances to be better defined by proper as a consultant in many other railway issues heritage of the already described car addiction feasibility studies. Among all of these future regarding the S-lines network. which makes it sometimes difficult to save infrastructure projects, extension and new spaces and paths to boost the trams’ speed. services it’s possible to report the following TRAM NETWORK Increasing the average speed is the main rail works, some being prioritised according objective for future network developments. to studies’ output, financing possibilities and Milan has the most extensive tram network in As said, Milan’s tramway network is more political will: Italy and is among the world’s largest, totaling than 140 years old, however MM has worked 230 km and 18 lines. since the ‘90s on all the new high capacity Metros tram segments and extensions, reaching The fleet consists of more than 500 trams metropolitan municipalities out of Milan • M1 southwest extension to Baggio, 3 km operating daily, 5 depots and an operating City borders. Also new forthcoming plans, and 3 stations center; all Milan’s tramways have a wide 1.445 regarding a new “inter-peripheral” north • M4 east extension to Westfield Milan mm gauge and electric supply line above from beltway line and the Brianza (north-eastern “Porta Est” (new East gate HSR station); pantographs. metro area of Milan) extra urban lines • M5 north extensions to Monza, about 12 refurbishment are managed by MM. km and 11 stations It hasn’t been always like this as the tram • M5 west extension to Settimo, 4,5 km and network dates back to 1876 and started with A quick note about airports rail links: Milan’s 4 stations horse powered cars, soon followed by steam intercontinental airport MXP and international ones. airport LIN are both linked by rail to Milan Railways thanks to rail infrastructure projects planned In recent years, the historical network by MM. Also planned is the third satellite of • New suburban lines (curtailed in many parts following the MXP Terminal 1: a 12 km rail branch from • New urban stations, especially along rail development of the metros) has been Busto Arsizio (northwestern metro area) is beltway supplemented by new modern tramways, serving the terminal 1, recently extended by • New HSR East gate station mainly to connect suburban areas with the city FNM to Terminal 2 too with another station, centre and/or metro stations. new 15,2 km and 21 stations M4 line will have Tramways the second as first eastern terminus. Both One of them is metrotranvia Milano–Cinisello, infrastructures, to be implemented, help Milan • New inter-peripheral north belt line about which connects with the neighboring city of to achieve the EU goal to rail-link all major 13-14 km long; Cinisello Balsamo, that has a population of airports. Another rail link to the international • Milan – Brianza Extra urban tramway to 76.000 people. Approaching Cinisello the low-cost airport BGY and a “loop connection” Limbiate, about 12 km long route is relatively easy and fast. Although, as completing the existing MXP rail link are • Milan – Brianza Extra urban tramway to the line penetrates the historical city centre of under planning at the regional Lombardy Seregno, about 17 km long Cinisello, it runs through narrow streets. These headquarters. were freed from most road traffic, whereas the city utilities (sewerage, water and gas systems, FORTHCOMING AND FUTURE Other extensions and the new M6 line, as cabling of any kinds) do not have other routes DEVELOPMENTS pointed out by PUMS, have to be seen on a but the underground of these narrow streets. longer term. As most utilities are not allowed to stay in Mobility in the Milan Metro Area has been MM has worked as consultant in the making the ground underneath the tram tracks, planned by PUMS, Piano Urbano per la of PUMS and it’s currently setting most of the the construction of the tramway required a Mobilità Sostenibile (Sustainable Urban quoted infrastructures feasibility studies, plans walkable tunnel to be built beneath the streets Mobility Plan), the first mobility plan in Italy and projects. to host as many utilities as possible. having added the ‘S’ for sustainability to the used Italian acronym PUM. In fact, PUMS aims A 1,6 km extension to Rozzano, the metro to complete the sustainable revolution basing area first ring Municipality south of Milan, is on three main keystones: currently under completion. • Extend public transport coverage and Rolling stock is various, from an historic 13,9 accessibility m long single car “Carrelli” carrying up to 130 • Shift modal split enhancing green mobility pax to 7 articulated cars “Sirio”, 36 m long able and discouraging cars and carbon to carry 285 passengers at 6 pax/m². Peak emissions frequencies get up to 180” on network’s main • Recover public spaces segments, therefore capacity locally goes up to 5.700 pphpd.

100 JOURNAL OF PROCEEDINGS TECHNICAL

Northern Line AUTHORS:

Suresh Thiagarajan extension project London Underground

BACKGROUND PLANNING AND FUNDING in this plan. With the launch of Night Tube in Initial transport options and feasibility were 2016, the Northern Line has seen an increase The Northern Line Extension (NLE) is a project developed in 2008; this concluded that an in its train frequencies and combined with being delivered by TfL for London Underground extension of the Northern Line was the the upgrade of the signalling infrastructure Limited (LUL). The project is a continuation best practical means to deliver the level of will deliver a 20 per cent increase in capacity of the existing Charing Cross branch of the accessibility and capacity required to unlock through central London in peak hours. This Northern Line from the Kennington Loop to the VNEB development aspirations. Other investment paves the way for even greater train a new terminus south of Battersea Power options considered included bus routes, Light frequencies for the 2020s. Additionally TFL Station. See image 1. Rail and London Underground extensions to also plans to improve capacity at critical tube the Victoria Line (Vauxhall), Bakerloo Line stations including Bank, Camden Town and The project is one of the largest construction (Elephant & Castle) and District Line (Sloane Elephant & Castle. projects in London and the first new addition Square). to the London Underground tube network A Transport and Works Act Order (TWAO) since the Jubilee Line Extension (opened The delivery of the NLE will also help address required to construct, operate and maintain in 1999). It will encourage growth in the some of the capacity constraints being faced the new stations and railway was prepared economy for London and the UK by facilitating at Vauxhall, by providing the public with an and submitted in April 2013. The TWAO was sustainable regeneration and development of alternative means of travelling to and from this granted in November 2014 supporting delivery the Vauxhall Nine Elms and Battersea (VNEB) area. The extension is largely focused on trips of the Mayor’s key strategies including: Opportunity Area; this includes the creation of to / from central London (west end), although a major new residential, business and leisure an interchange to the Northern line City branch • supporting economic development and district. London has limited opportunities for will be possible at Kennington Station. population growth accommodating large scale development; the • enhancing the quality of life for all ‘Opportunity Areas’ are London’s major source Installing the new infrastructure will support Londoners of brownfield sites which have significant a peak service frequency of up to 30 trains • improving the safety, security and capacity for development. These development per hour (tph) into the new Battersea Power transport opportunities for all Londoners opportunities include investigating improved Station. The NLE will also help provide • reducing transport’s contribution to local public transport access. Typically an significant improvements in travel times to climate change and improving resilience opportunity areas can accommodate at least central London with a reduction of up to 64% 5,000 jobs, 2,500 new homes along with other expected between the Nine Elms area and the The project is externally funded by the Greater supporting facilities and infrastructure. The west end. London Authority with the anticipation that the NLE project supports the VNEB area and aims VNEB Opportunity Area developer Section 106 to help create 18000 new homes and 24000 Transport for London has a significant and Community Infrastructure Levy Section new jobs. See image 2. investment programme over 10 years to (CIL) contributions, incremental business rates upgrade the Northern Line. Extending the line and sale of the over site development at Nine to Nine Elms and Battersea is just one step Elms station will contribute to the funding. The project is targeting a completion date of 2020.

STAKEHOLDERS AND ENVIRONMENT

TfL worked with numerous stakeholders to achieve satisfactory arrangements to enable the construction of this urban project. Key stakeholders along the route include but are not limited to, Battersea Power Station Development Corporation (BPSDC), Barratt Homes, Network Rail, Sainsburys, three London borough councils, Royal Mail Holdings, Battersea Dogs and Cats Home and local residents.

A requirement of the TWAO process was the production of an environmental statement and a variety of commitments to minimise the impact of the project both during construction Image 1: London Underground tube map

101 TECHNICAL JOURNAL OF PROCEEDINGS

and the ongoing railway operations. A key DESIGN AND BUILD (D&B) GEOLOGY commitment was to minimise the amount of CONTRACT tunnelling and excavation spoil removal by Local geological investigations were road; with a commitment to remove as much The main D&B contract was awarded to undertaken and historic data validated. spoil as possible from Battersea site by barge Ferrovial / Laing O’Rourke (Flo), a Joint Ground conditions on the site comprise of down the river Thames. This was achieved Venture group, in September 2014; this Made Ground with varying thickness underlain by introducing elevated conveyor across the included all civil engineering and building by river terrace deposits. Locally a layer of Battersea Power station site to enable loading works, plus track works and associated alluvial deposits is encountered in between of barges. The project successfully excavated mechanical & electrical infrastructure (MEP). these two layers due to its proximity to river and removed 845,299 tonnes of spoil via 701 The additional railway systems works which and its former course. The underlying geology barges, which resulted in 47000 muck away include signalling, communications, HV power comprises of London clay which is underlain by lorries taken off the London streets saving feeds etc. will be delivered under existing LU/ the Lambeth Group materials. The new tunnels 2640 tonnes of CO2. PFI contracts. lie predominantly in the London clay with a 300m section of the TBM driven tunnels and The ground borne noise levels originating from The civil engineering and track infrastructure one hand mined cross passage partically in the the new railway operations were predicted primarily comprises of: challenging Lambeth Group. See image 4. to result in adverse effects that could cause disturbance to properties above the route. To • Two 3.2km running tunnels connecting TUNNELS reduce the effects of the ground borne noise, the existing Kennington station to a new vibration isolating track form was specified. station at Battersea (Battersea Power The tunnelling works were split into 6 work The chosen track system will also reduce the Station) via a new intermediate station at packages consisting of bored running tunnels, operational ground borne vibration effects for Nine Elms overrun tunnels, TBM launch tunnels, step both the day and night operations. Ground • Two ventilation and intervention shafts plate junctions (SPJ) and cross passages. borne noises from the temporary railway was located at Kennington Green and Various tunnelling techniques were used to controlled following current best practice by Kennington Park deliver these works which included the use monitoring noise and vibration emissions, • Four new cross passages on the existing of tunnel boring machines, hand excavation checking against permissible levels as agreed platforms in Kennington Station with timber headings and machine excavated with the local authority through section 61 • Three new cross passages connecting tunnels using sprayed concrete lining (SCL) agreements and using local speed limits for the North and Southbound tunnels plus some lengths of spheroidal graphite the temporary railway. Ground settlement as a • Permanent Way; plain line track, two iron (SGI) segments. TBM and segment result of the NLE construction has the potential single lead connections to the Kennington construction is considered most efficient for to affect a large range of buildings and utilities loop, Scissors crossover at Battersea relatively long drives but has a high initial directly above and along the route of the NLE. • Power supply and ventilation cost with the construction of the TBMs. SCL The predicted settlements were assessed infrastructure construction is effective for shorter tunnel on the basis of volume loss and the resulting drives, which can be several hundreds metres settlement negligible due to the use of EPB See image 3 long, and where tunnel profile changes TBM’s for the tunnelling works. The impact frequently. Hand mining is used for tunnelling of the resulting settlements on buildings and in restricted spaces where mechanical utilities still are continually monitored. excavation is difficult; i.e. for working around existing tunnels.

Image 2: Vauxhall Nine Elms Battersea

102 JOURNAL OF PROCEEDINGS TECHNICAL

Image 3: Proposed extension overview

BORED RUNNING TUNNELS

The running tunnels were constructed using two Earth Pressure Balance machines (EPBM). The twin bore tunnels have an internal diameter of 5.2m; the largest on the London Underground network. The spaced proofed design accommodated future enhancements of infrastructure as well as a one metre wide walkway to facilitate emergency services intervention and passenger evacuation. See image 5.

Due to the geological challenges (in particular the proximity to the Lambeth beds), EPBM’s were the preferred tunnelling method for the main running tunnels. NFM Technologies were selected by FLo to manufacture the two new 6.0m diameter EPBM machines at a cost of circa £10m each Both TBM drives were completed in just over 6 months Image 4: Geology constructing over 2.5km (southbound) and 2.3km (northbound) of tunnels from Battersea, concluding in the two Kennington Shaft structures. See image 6.

The TBM tunnels structure consisted of 250mm thick concrete bolted segments, reinforced with steel and synthetic fibres with ring length of 1.5 metres. Segments were manufactured off site by Morgan Sindall.

Three cross passages were also constructed between the running tunnels; required for operational evacuation purposes. These were constructed in the London clay using timber headings and SGI segments.

OVERRUN AND LAUNCH TUNNELS

The overrun and launch tunnels were constructed either side of the Battersea station box to facilitate the train safety requirements and to launch the two EPBM’s respectively. The 22m long overruns have an internal diameter of 5.2m and are required beyond the end of the platforms at Battersea Power Station to provide a safety zone should a Image 5: Tunnel space proofing diagram

103 TECHNICAL JOURNAL OF PROCEEDINGS

Image 6: TBM launch

Image 8: Step plate junction section Image 7: Tunnel Cross passage

train be unable to come to a complete stop From these SCL tunnels the step plate works 16 week platform closure between May and within the station. The launch tunnels (length involved excavating and supporting the old September 2018. Fit out works and completion 77m with varying diameters) were required tunnels in sections within the new tunnels. The is due prior to NLE opening in 2020. Train to provide space for a full earth pressure construction works required careful tunnelling services continued to operate on the Northern balance mode launch of the TBMs outside of and excavation including hand mining, SCL Line through the station for the duration of the the Battersea station and crossover boxes, to and SGI tunnelling techniques; continually works. See image 11. mitigate the programme impact associated with supporting and monitoring the existing cast assembling and launching the TBMs from the iron tunnels and tracks was essential. VENTILATION SHAFTS AND boxes. It also provides for wider entry into the The construction works were completed in 14 HEAD HOUSES running tunnels for trains leaving the station months whilst maintaining operational running through the crossover. of the Northern Line. The requirements and functionality of the shafts and associated head houses are STEP PLATE JUNCTIONS KENNINGTON STATION CROSS essential for the NLE project in terms of PASSAGES operations and safety. The tunnel ventilation Constructing the two new step plate junctions and draught relief are vital to maintaining involved challenging tunnelling works to Following the introduction of the NLE, acceptable temperatures and safe evacuation connect the new extension to the existing Kennington station will become a key in the event of an emergency; the extension Northern Line at the Kennington Loop. The interchange station for passengers wishing cannot operate without the two vent shafts. original Northern Line was built circa 1890 to switch between the Charing Cross or Bank To satisfy this requirement four number fans with the Kennington loop (3.81m ID cast branches in addition to the passengers using and associated power, communications and iron tunnels) constructed in1924. The new Kennington. A 2011 passenger flow model MEP equipment will be located in each shaft connections to the northbound and southbound undertaken by London Underground suggested to afford the ventilation, cooling and smoke tunnels were constructed using a step plate severe congestion on platforms and existing control within the tunnels and to allow for a junction encirclement of the existing tunnels. cross passages is likely due to the expected protected pressurised access and egress route This is a traditional tube tunnel construction gradual increase in the number of passengers for emergency services and passengers. The that enables a junction / split from one tunnel interchanging at Kennington Station. As a shaft structure is constructed using secant to two tunnels over a stepped increase in result, to improve passenger flows between the piled walls for the main box and circular shaft, tunnel size. The Kennington junctions are platforms, four new cross passages are being SCL for the tunnel interfaces and precast constructed within three diameters of SGI built. The design of the cross passages is in concrete and in-situ secondary structures. See tunnel; which are 5.2m, 6.5m and 9.5m. See keeping with the heritage status of the station image 12. images 8 and 9. which is a Grade II listed building. See image 10.Using hand tunnelling, timber headings To enable the new connections, two 5.2m and SGI segments to connect the existing ID SCL tunnels were constructed from the cast iron and masonry tunnel interfaces, the Kennington shafts and terminated adjacent tunnelling works were carried out during a to the existing Kennington Loop CI tunnels.

104 JOURNAL OF PROCEEDINGS TECHNICAL

NINE ELMS STATION AND TRACK, ALIGNMENT AND avoided by construction traffic and the effects BATTERSEA STATION CONSTRAINTS of the operational railway had to be minimised.

Track and tunnel alignment design had to take The two new stations at Nine Elms and The alignment design was dictated by a into account the following: Battersea will be integrated with the considerable number of constraints. Local surrounding local area, providing ground level geology is most significant for a deep tube • Safety entrances that are fully accessible with a step- tunnel railway and in London it is highly • Minimise journey time free route between street and trains. The new desirable to keep as much of the subsurface • Clearances stations will mean thousands more people will railway in the local London Clay strata as this • Quality of ride be within easy walking distance of the Tube is an ideal tunnelling medium. However in • Maintenance network. Both stations are designed to be the established urban infrastructure of south • Minimal ground borne noise and vibration integrated over site developments. west London there are the challenges of • Ease of construction Nine Elms station box is constructed using avoiding existing buried structures including secant piled walls with a lining to ensure London Underground lines, foundations, (piled The Initial TWAO alignment design was for effective water tightness. The station has been foundations in particular), service tunnels and planning purposes and the train speeds were constructed using ‘Top Down’ construction sewers. not as high as LU operations would like. The incorporating precast concrete beams with in- TWAO ‘planning’ process set the Limits of situ slabs for internal structures. Construction The objective was not to go too deep to Deviation which meant there was not much of the station commenced in August 2015. See encounter the tricky Lambeth Group strata scope for re-alignment which resulted in a image 13. underlying the London Clay (there is a history concession to LU standards. of encountering water under pressure in the The new terminus at Battersea is integrated Lambeth Group) and to have the stations as The following LU design standards were within the Battersea Power Station high in the ground as possible to reduce the adopted: development and the design has required close distance to street for customers. stakeholder engagement with the developer • Curves, - smallest radius 400m radius BPSDC. Due to its close proximity to the river Surface / street level constraints included (min 300m agreed due to LOD) Thames the design incorporated diaphragm minimising the impact on public spaces, listed • Gradients, - maximum 2.00%, minimum wall construction with precast concrete and in- buildings and local businesses. A significant 0.250; level through stations situ internal secondary elements. Construction constraint was to avoid the sensitive cricket • Cant, - maximum of 125mm. commenced in March 2015. See image 14. venue at the Oval. There are also some large • Line Speed - both lines Vmax. 90km/h areas of mixed housing which needed to be

Image 9: Step Plate Junction completed Image 10: Station Cross passages

Image 11: Completion of civils work for Station Cross Image 12: Kennington Green Shaft Passage C

105