TECHNICAL ARTICLE

AS PUBLISHED IN The PWI Journal January 2020

VOLUME 138 PART 1

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PLEASE NOTE: Every care is taken in the preparation of this publication, but the PWI cannot be held responsible for the claims of contributors nor for the accuracy of the contents, or any consequence thereof. HS2 Gauging – The Uniform Structure Gauge (USG)

AUTHOR INTRODUCTION EXAMPLES OF TYPICAL AREAS WHERE GAUGING IS REQUIRED Gauging is an integral part of any railway Klaus Pajung system. This paper describes the HS2 approach Typically, gauging is required for the following Senior Permanent Way to gauging and it shows how HS2 established scenarios: Design Engineer 4 different Uniform Structure Gauges (USG) which suit their specific . The paper CLEARANCES TO STRUCTURES AND Klaus is a Senior also provides an overview on how USGs are EQUIPMENT Permanent Way calculated. Design Engineer with The most common structures and equipment to an overall experience BACKGROUND stay clear of comprise: of 17 years. He is a Chartered Engineer in Germany (Diplom Every Railway Infrastructure manager has to 1. Overbridges (soffit and abutments) Ingenieur - FH). ensure that the type of rolling stock on their system can be run in a safe manner from a spatial 2. including evacuation walkways Klaus came to the UK in 2005 and stayed perspective, ie the don’t hit parts of the and associated equipment (e.g. ventilation with Atkins in Birmingham for the following infrastructure or other trains. This is achieved fans, OLE, cable troughs etc.) 3 years. There he mainly worked on S&C by means of ‘Gauging’. For HS2 gauging the schemes at various design stages. TSI is applicable which refers to Euro Norms 3. Lineside equipment such as signals, (EN) to determine structure gauges for new and masts, posts, speed boards etc. Klaus then moved on to Halcrow in London interoperable infrastructure. who he is still with, (now Jacobs). There he 4. Platform offsets. Platforms are special worked on NR schemes at various GRIP In general, a structure gauge is an envelope structures, as trains have to pass them stages, TfL projects and international describing an area that must not be infringed by at a relatively close distance. This is projects. any infrastructure or lineside equipment under because of a ‘conflict of interest’ between any condition (see figure 8). structural clearances and appropriate He is currently seconded to HS2 where he stepping distances. A sufficient clearance is looking after the alignment including Even though EN calculation methods for structure to the platform is essential and has to be the associated standard, the S&C geometry gauges are predetermined, the Infrastructure guaranteed for stopping and potentially standard and the gauging standard. manager has options to create different structure for fast, non-stopping trains. However, for gauges that suit their specific needs. For passenger friendly stepping distances, example, they might want to have a ‘Uniform trains need to be as close to the platform Structure Gauge’ (USG) which is applicable to as possible. specific areas such as tunnels, the open route, stations, station approaches, depots etc. TRACK SPACING AND PASSING CLEARANCES The following points will give the reader some general background on gauging. Track spacing is the distance between railway tracks. For NR, a standard spacing is 1970 mm WHAT IS GAUGING? between the running edges of the rails on straight track which equates to 3.405 m between track Gauging is the process for ensuring that trains centre lines (CL). For HS2, the track spacing, which are used on a specific section of track and measured from CL to CL, is dependent on the railway infrastructure are compatible in terms speed. This is because with increasing speeds, of spatial relationship. These days gauging is a aerodynamic considerations must be taken into scientific method which creates an artificial consideration. HS2 uses track spacings which envelope that is greater than the physical train, are compliant with the TSI and which are similar taking into considerations items such as track to other European high-speed administrations. geometry and speed amongst others. Therefore, no analysis needs to be undertaken to prove these track spacings are sufficient. As the Independent of the gauging method used (see TSI only covers speeds of up to 350 km/h, a track further below), the resultant envelope determines spacing of 4.7 m has been specified by HS2 for the space that must not be infringed on by any speeds between 350 km/h and 400 km/h. This is part of the infrastructure or line side equipment. 0.2 m wider than the track spacing required by the The resultant envelope might be called Structure TSI for speeds > 350 km/h. HS2 appreciate the Gauge (eg in the EN) or the Swept Envelope fact that future improvements in aerodynamics in other standards. The latter usually requires might have to be achieved so the speed could be additional distances (clearances) to be kept to the raised to 400 km/h should this be implemented at envelope. some stage in the future.

34 FOULING POINTS HS2 GAUGING

Fouling points (FP) are points between the HS2 have 4 USGs as described below. This is through track and the diverging tracks of a to avoid having a single and very large USG turnout or crossover arrangement beyond which would use worst-case input values from which trains would collide if both tracks were across the system. occupied at the same time. To establish the appropriate position of fouling points the On the one hand such a single structure gauge relevant structure gauge (Limit Gauge for EN would be user-friendly for the Infrastructure gauging) must be calculated. See Figure 1 as manager. On the other hand, an oversized an example. single structure gauge would mean that structures or lineside equipment would have GAUGING METHODS to be further away from the tracks, therefore potentially increasing footprint and cost. This is Figure 1: Fouling point as per Spanish gauging There are different gauging methods which are in particularly true for tunnels as with a single standard for through speeds >120 km/h. described as follows: route-wide USG the diameters of many tunnels would have to be increased. ABSOLUTE GAUGING This section provides some background Absolute gauging is mainly used on existing information and detail on various aspects of infrastructure. It is a full assessment of HS2 gauging. clearances on a section of existing track between the vehicle and fixed infrastructure USE OF THE SPANISH GAUGING and the vehicle and vehicles on adjacent STANDARD tracks. These days absolute gauging is executed by means of computer programmes HS2 gauging is based on the Spanish gauging like ClearRouteTM, DGauge etc. These standard (FOM/1630/2015) which is well programmes consider the whole suite of rolling established and has a proven record for high stock used on a section of track with all their speed railways. It is based on EN15273 and in characteristics (static envelope, suspension, fact, is a further development of the EN which distance etc.). They also consider track ‘puts meat on the bone’ in sections where the Figure 2: Typical ClearRouteTM output for related properties (track form, curvature, , EN is rather vague. For example, EN15273- structure and passing clearances speed etc.) and wear, likely track movements 3 (section 5.5.3) provides two examples of etc. to calculate a swept envelope. This scenarios for the calculation of USGs which swept envelope is an enlarged version of the might be considered: static envelope and used by the software to determine clearances to the existing • The worst-case situation: Worst-case infrastructure. Most railway administrations input values are considered such as will define a clearance to the swept envelope smallest radius, the maximum cant or that has to be met. For example, NR define a cant deficiency etc, clearance of 100 mm to the Swept Envelope as ‘normal’ in many cases. Figure 2 is a typical • Defining of the gauge with two profiles: Table 1: HS2 Uniform Structure Gauges ClearRouteTM output showing structural and One profile applicable on a straight or passing clearances for a wide range of rolling curved track with very large radii and no stock. cant. Another profile on a curved track designed on the basis of the worst-case COMPARATIVE GAUGING cant and radius situation.

Comparative gauging is the process of The Spanish gauging standard describes comparing the swept envelope of a new the second scenario in detail; considering 8 vehicle with the swept envelope of a vehicle or different scenarios as a result (see calculation vehicles which have demonstrated to comply section for more detail). with gauging requirements of a track section. This way conclusions can be drawn on whether The HS2 calculation methodology is based on this new vehicle can be used on a specific this second scenario. route section or not. TYPES OF GAUGES REQUIRED FOR HS2 DEFINED GAUGE METHOD AS PER EURO GAUGING NORM EN 15273 HS2 use the following types of gauges in their The defined gauge method described in EN standard: 15273 (Parts 1 and 3) is split into 3 main methods: • Uniform Structure Gauge (USG). The Figure 3: Overlay of area-wide USG (black) USG is used to determine the distances A) The static method is used for specific, non- and local USG (red) to be kept to between structures and interoperable networks. equipment and to the trains and therefore to the tracks. HS2 developed 4 different B) The dynamic method is used on certain USGs for different areas of application networks with the aim of optimising the space along the route These are summarised available for sizing non-interoperable vehicles. in table 1. More explanation on how HS2 arrived at these is discussed later in this C) The kinematic method is used in Europe article. mainly on interoperable networks. It is therefore used by HS2 and discussed further Figure 4: Principle of EN structure gauge in this paper. determination

35 • Structure Installation Limit Gauge. This The Uniform Structure Gauge (USG) is a CALCULATION OF THE UNIFORM gauge is used for platform offsets, track specific case of a SING. It is calculated in the STRUCTURE GAUGE intervals and fouling point considerations. same way but using worst case calculation It is not discussed in this article. input values occurring in a specific area of In general, calculations are carried out for all application, e.g. all open route sections. 8 points of the reference gauge (see figure • Pantograph Gauge. This gauge 5) for both horizontal and vertical directions. determines the space required for the The term USG will be used in this article for However, there are many exceptions to this pantograph structural and electrical simplicity unless a clear distinction needs to be rule, in particular, for points below the rotation clearances. It is not discussed in this made between SING and USG. centre height (taken as 0.5 m). Furthermore, article. many vertical calculations are undertaken for USGs are structure gauges describing a Point 1 only. In their gauging standard, HS2 allows local theoretical maximum train envelope which USGs to be developed in specific locations must not be infringed on by any structure Calculations vary depending on whether points where none of the four HS2 USGs can be or equipment. They are developed from a are on the inside or the outside of a curve. applied. For example, both USGs for tunnels reference profile (see Figure 5). The size of Furthermore, different speed scenarios are (USG 1 and 2) allow for a limiting maximum the reference profile is increased horizontally taken into consideration with v = 0 km/h and cant of 160 mm. Should a designer propose an and vertically to be a USG. This is achieved v = vmax. A more detailed description on exceptional cant of say 180 mm in , then by adding associated rules which take into scenarios taken into consideration is provided they will have to calculate a local USG using all consideration various factors such as speed, later in the article. worst-case input values relevant for the section geometry, track form etc. that are not part where the 180 mm of cant are applied. They of the reference profile. The principle of this Once calculations are completed, a must then compare the resultant local USG process is summarised in Figure 4. symmetrical USG is created using the worst with the area-wide USG (in this case USG 1 or X and Y values of all scenarios. X and Y USG 2). If the local USG is outside or partially For the kinematic gauging method, EN 15273 values, e.g. for the Reference Profile, are the outside the area-wide USG (see example in mandates the use of kinematic reference ‘coordinates’ shown in Figure 5. For example, figure 3), then the local USG must be used. gauge GC for the upper part (h>400 mm) the coordinates of Point 1 are 1.540/4.700. Otherwise the area-wide USG must be applied. and GI2 for the lower part (≤400 mm). These The following calculation methodology has reference gauges represent the outermost been simplified to not exceed the scope of this THE KINEMATIC GAUGING METHOD boundary to which a train manufacturer can article. design taking into consideration maximum The kinematic gauging method is used to load and suspension dissymmetry. The actual A) REFERENCE GAUGE create structure gauges called Structure as-built train envelope must fit within the static Installation Nominal Gauges (SING) amongst reference GC gauge. The kinematic method, BS EN15273-3 other gauges which are not discussed in this mandates the use of kinematic Reference article. The GC gauge is applicable to all HS2 rolling Gauge GC for the upper part (h>400 mm) stock which will comprise of two types of and GI2 for the lower part (h≤400 mm) the passenger trains; (‘Captive’ trains for use on boundary between which is represented by the HS2 network only and ‘Classic Compatible’ point number 4 in Figure 5. trains which are also used on the NR network). Furthermore, this will be applicable to any B) INPUT VALUES maintenance trains on the system. As Classic Compatible trains are smaller they do not use Input values are described in EN15273-1 and GC Gauge, therefore they don’t have to be EN15273-3 and selected by the Infrastructure gauged separately on the HS2 system (but manager as appropriate. HS2 made the they do on NR infrastructure). conscious decision to only allow input values Table 2: Overview of scenarios taken into which were at least in the limiting range considerations for a USG. The kinematic gauging method is simpler than as per the HS2 Track Alignment standard the absolute gauging method described above. regarding cant and cant deficiency. Therefore, Its key advantages are: if designers use exceptional design values they are no longer ‘covered’ by the HS2 USGs • User friendliness. No specialist software and must calculate an area specific USG as is required to calculate clearances once described above. USGs have been determined. The USG, for example in form of a CAD file, can be Input values are as follows: copied or referenced into a cross section. This way infringements can be detected 1. Track form (ballasted track or slab track) easily. 2. Track quality (very good or ‘other’). For HS2 the assumption is that after • Low number of USGs required for the installation the track quality is very whole system. USGs can be applied for good and that it is maintained to this large areas of the railway infrastructure standard. Quality is based on track and don’t have to be calculated for quality measuring coach outputs. For various individual geometrical constraints, depots ‘Track quality other’ has been rolling stock etc. assumed as depots are usually not as well maintained as main lines. As a disadvantage, USGs are usually more 3.

conservative than swept envelopes calculated lnom : Nominal (1.435m)

using the absolute gauging method. However, RH : Minimum horizontal curve radius

on a newly designed railway this isn’t normally RV: Minimum vertical curve radius a major concern. (hog or sag)

Dmax /Imax: Maximum cant and cant deficiency Other factors which are less commonly known 4. Speed Figure 5: Kinematic reference gauge

36 Figure 6a: Typical PT point (here to inside of curve). Figure 6b: HS2 “PT line”.

C) ASSOCIATED RULES AND FORMULAE M3b additional value which is to be the outside it takes into determined the infrastructure consideration cant deficiency. Associated rules take into consideration manager. It covers specific aspects various phenomena that are not part of the regarding the use of vehicles or ∑2h vertical displacements, also referred reference profile, therefore increasing its size. loads larger than those allowed to as ∑ V,V* , due to vertical track This way they will enlarge the reference profile by the gauge, aerodynamic and position, vertical cant deviation, horizontally and vertically to be a USG. other considerations (0mm for vehicle dissymmetry and HS2) oscillation (Δhx in point F. below). D) LATERAL CALCULATION OF USG The sum of the allowances is POINTS E) VERTICAL CALCULATION OF USG determined for point PT only (Point POINTS 1). In general, the lateral points of the USG are determined by calculating Associated Rules In general, the vertical points of the USG are M3h similar to the horizontal calculations which increase the width of the reference determined by calculating Associated Rules this term refers to an additional profile. Calculations are done for all points of which increase the height of the reference value which is to be determined by the reference profile unless stated otherwise. profile. Calculations are done for all points of the infrastructure manager (0 mm the reference profile unless stated otherwise. for HS2). In general, the width of the USG is calculated The height of the USG is calculated using the using the following equation and terms. following equation and terms. F) ADDING-UP RESULTANT HORIZONTAL However, different scenarios have to be AND VERTICAL Σ2 ALLOWANCES considered, some of which will change this However, as described in point G. below, generic formula (as described in point G. different scenarios have to be considered for For the SING, Σ2 allowances are added up below). the calculation, for some of which the signs of arithmetically according to the formulae below. individual summands will change. This is as per the Spanish gauging standard The last four terms denote the Associate which is advanced in its interpretation of the Rules. The last four terms denote the Associated European gauging norms and which is also Rules. used for high speed. bnom i,a ≥ bcr + si/a + qsi/a + ∑2b + M3b

hnom ≥ hcr + ΔhRv + ΔhPT + Σ2h + M3h 1. Horizontal Σ2: horizontal associated rules vertical associated rules where: where: 2. Vertical Σ2:

i/a factors which are to the inside to hnom vertical coordinate (height) of USG inside (i) or outside (a) of a curve point

bnom i,a lateral coordinate of USG point hCR reference profile height The resultant sums feed into the eight different USG scenarios to be considered which are bcr semi-width of the kinematic GC ΔhRv vertical raising or lowering on a described below. reference profile vertical curve. This is relevant for the upper part only. For points at the G) CONSIDERATION OF DIFFERENT si/a additional overthrows same level or above the maximum SCENARIOS FOR THE FINAL UNIFORM width (i.e. Points 1 and 2), resultant STRUCTURE GAUGE qsi/a quasi static roll, calculated above values are added, for points below height of rotation centre (0.5 m) this level (i.e. Points 3 and 4) values To arrive at a final USG, eight different are deducted. scenarios have to be considered. For each of

∑2b horizontal displacements (also these scenarios specific associated rules are

referred to as Σj,j*) due to ΔhPT super elevation of the upper parts calculated. The Spanish gauging standard horizontal track position, horizontal due to the vertical effect of the roll states in section 3.3 that the following cases cant deviation, vehicle dissymmetry (only relevant for Point 1). This term have to be considered for both vehicles at

and oscillation (Δbx in point F depends on the angle αPTi,a which maximum speed and static vehicles: below). In the EN, this is is rotation of the gauge due to the also referred to as allowance M1 + quasi-static effect. This term can 1. Maximum lateral displacement with its M2 which define ∑2 differ between the inside of the compatible displacement perpendicular curve and the outside of the to the running surface. This scenario is curve. For the inside, it takes into relevant for curved track. consideration cant whereas for

37 2. Maximum displacement perpendicular to In theory, establishing the outermost contour mandatory. This is done by selecting the worst- the running surface with its compatible by connecting all No. 1 Points of the 4 USG case X and Y values for each of the 8 points on lateral displacement. This scenario is scenarios (to both the inside and to the outside) either side and applying them to both sides. relevant for straight track and large radii. would suffice to create a USG. However, this would create a rather complicated shape and HOW TO APPLY THE UNIFORM Furthermore, as per section 5.2.1.3 of could therefore not be user friendly for the end- STRUCTURE GAUGE EN15273-3, the quasi static effect must be user who is the Infrastructure manager. considered taking into consideration speeds: USGs are applied perpendicularly to the In general, the PT point is determined once plane of the rails as shown in figure 7. The A) “outside the curve, under the cant deficiency the 8 USG scenarios described above have calculations to determine the USG are such effect”. This is relevant for the maximum been calculated. It is established separately that the cant is not taken into consideration speed. for the inside (scenarios 1-4) and the outside twice with this method. B) “inside the curve, under the cant effect”. (scenarios 5-8). The PT point is typically This is relevant for a stationary train (0km/h). determined by intersecting the outermost DEVELOPMENT OF THE HS2 UNIFORM vertical line of all scenarios beyond Point 1 STRUCTURE GAUGES However, to cover all possible cases, scenarios and the top horizontal line beyond Point 1, see A) and B) are calculated for both speed figure 6a. However, there is no rule stating Every Infrastructure Manager will eventually options, which is also in line with the Spanish that it must be done this way. Whereas this have to develop a USG or USGs which gauging standard (section 3.3). This way 8 methodology provides a smooth USG envelope suit their infrastructure needs. This section scenarios are created: it also increases its size. describes how HS2 determined their USGs by applying the steps described below. A) Case 1 above to the inside and the outside To minimise the size of the USGs, whilst having of a curve, both at a speed of 0 km/h and at the a smooth envelope at the same time, HS2 A) DETERMINE AREAS WHICH COULD maximum speed (4 scenarios) decided to eliminate the top corner created by HAVE THEIR OWN USG. the typical PT method described above. This B) Case 2 above to the inside and the outside could be achieved by connecting all four No. After internal discussions within the HS2 of a curve, both at a speed of 0 km/h and at the 1 Points with a “PT line” such that none of the track team, initial areas as described below maximum speed (4 scenarios) points are outside this line (see Figure 6b). were selected. Each area is clearly defined The ’savings’ made in the top corners are and comes with its individual properties and Table 2 provides an overview of the 8 particularly relevant for areas where space is constraints. scenarios for which these formulae are to be limited, such as tunnels. For example, for USG used. 2 the area of the top corners is reduced by 1. Terminus Stations. Characteristic input approximately 100 cm2 on each side. values for these USGs were low speed, H) THE PT POINT no cant and no vertical curvature. It I) SYMMETRICAL USG was anticipated that this could lead to The PT point is an additional theoretical a relatively small USG which would be point in the top corner of a USG. Its aim is As stated further above, calculations vary beneficial for equipment close to the track to smoothen the USG that is created from depending on whether points are on the inside in station environments. the 8 scenarios described above. Where or the outside of a curve. To have a more user- the reference profile is concerned, Point 1 is friendly USG, it is made symmetrical at the end frequently referred to as the PT point as well. of the calculation process however, this is not

Figure 8: Resultant USG 3 (prior to calculation Figure 7: Application of the USG (canted track). of PT line)

38 2. Through platforms. At stations such as At this stage it became clear that some of the To finalise the USG, a PT point (or PT line) Birmingham Interchange, trains can areas investigated could be merged due to the still has to be calculated before making it pass a platform at speeds of up to 230 similarity of their calculation input values. For symmetrical and therefore complete. km/h. Typical input values for the USG example, cut and cover tunnels were similar to calculation were high speeds on wide 8.8 m and 9.1 m diameter tunnels. SUMMARY radii, no cant and no vertical curvature. C) CALCULATE INITIAL USGS FOR EACH The HS2 Uniform Structure Gauges were 3. Station approaches. Characteristic input AREA determined using EN15273 parts 1 to 3 as values for these USGs were relatively specified by the TSI. The Spanish Gauging low speed on tight curves with cant and Using the input values above, HS2 calculated Standard was used as a well-established vertical curvature. 8 initial USGs using an Excel based tool. interpretation of the Euro Norms. The USG calculation tool was developed 4. Open route. Input values for the USG in cooperation with one of the Engineering The EN mandates that the kinematic gauging calculation were based on worst-case Delivery Partners who are experts in the field. method is to be used for new and interoperable open route track geometry values By entering the input values, the spreadsheet infrastructure. with high speed, tight radii (horizontal calculates the associated rules for all 8 and vertical) and high cants and cant scenarios discussed in the calculation section HS2 determined specific areas within the deficiencies. (see table 2) and the resultant final USG. system and investigated their gauging specific Furthermore, it will also calculate the structure properties. As a result, 8 areas emerged for 5. Different types of tunnels. Input values installation limit gauge which is used for track which initial USGs were calculated. These for the USG calculation were based on intervals, the fouling point and platform offsets. USGs were then analysed and rationalised. As worst-case track geometry for all HS2 a result, they could be reduced to the final 4 tunnel types. These comprised bored D) ANALYSE RESULTS AND RATIONALISE HS2 USGs. tunnels with different diameters and cut & AMOUNT OF USGS cover tunnels which can be on both slab REFERENCES track or ballasted track. Once the results were available, the resultant 8 USGs were compared and grouped into similar EN15273-1 6. Depots. As one might expect, input categories. As a result, they were merged into European Norm BS EN 15273-2-2013+A1- values for this USG were low speed and 4 USGs as shown in table 1. Table 3 shows 2016, Part 1 tight curves without cant. All HS2 depots the results for the station approaches and are on ballasted track. the slab track tunnels to show their similarity. EN15273-2 They were eventually merged into USG 3 (see European Norm BS EN 15273-2-2013+A1- B) ANALYSE THE TRACK GEOMETRY IN figure 8). This was done by using the worst- 2016, Part 2 THESE AREAS TO DETERMINE INPUT case X values of the inside (i) and outside VALUES FOR USG CALCULATIONS (a) and Y values of the inside and outside. EN15273-3

X-values correspond to bnom and Y-values to European Norm BS EN 15273-3-2013+A1-

The input values required are speed, horizontal hnom discussed in the calculation section above. 2016, Part 3 and vertical radii, cant, cant deficiency and the The most relevant points for this exercise are track form (ballasted or slab track). Points 1i,a (highest) and 2i,a (widest), they are Instruccion Ferroviaria de Galibos highlighted in table 3. (FOM/1630/2015) Spanish Gauging Standard

TSI 1299/2014 Commission Regulation (EU) No.1299/2014 of 18 November 2014 on the technical specifications for relating to the ‘infrastructure’ subsystem of the rail system in the European Union.

ABBREVIATIONS

EN European Norm FP Fouling Point HS2 NR Network Rail SING Structure Installation Nominal Gauge TSI Technical Specifications for Interoperability (infrastructure) USG Uniform Structure Gauge

Table 3: X and Y values for station approaches and slab track tunnels

39