Challenge E: Bringing the territories closer together at higher speeds

ACHIEVING THE SAME HEADWAY WHILST INCREASING THE SPEED FROM 300 TO 360 KM/H

Christian AULAGNIER, Operation System Department Manager Julien SARRAZIN, Prospective Studies Expert in the Operation System Department SNCF Technical Direction, Saint-Denis, France

ABSTRACT

Increasing the speed of the enables to achieve better journey times and hence to increase the revenues thanks to the elasticity of the traffic to the journey time. Therefore the railway companies have a clear incentive to increase the speed of their trains. On the other hand the augmentation of the travel speed generally leads to a rise in headway between two trains following each other all other things being equal. This study consisted thus in investigating the possibility of keeping the same headway whilst increasing the speed from 300 to 360 km/h. It was first necessary to establish the reference situation with a travel speed of 300 km/h on a high-speed line equipped of the last current national railway system then to determine all requirements in order to achieve the same performance at 360 km/h thanks to the ETCS L2 signalling system as those obtained currently. A braking distance to meet at 360 km/h had to be calculated in particular regarding signalling system and rolling stocks abilities. Therefore reasonable assumptions on what could be specifications of new rolling stock about for instance length, axle load, number of bogies and number of powered ones, aerodynamic characteristics, electric braking characteristics linked to the traction effort curve and pneumatic braking characteristics had to be made in order to define both service and emergency braking that would fulfil at least the minimum distance braking requirement previously found. The last step was to check whether those were adapted to main scenarios that could be encountered on a high-speed line at 360 km/h according to methods calculations of the ETCS curves and operating conditions. The results provided by this study seem to suggest that it is possible to increase the speed of the trains from 300 km/h to 360 km/h without falling capacity on high-speed lines.

KEYWORDS

TGV - TVM – ETCS - Headway - Capacity - High-speed line - Breaking curves

1. INTRODUCTION

Without even thinking about reinforcing the prestige of a railway company, what is at stake in the increase of the top speed is for sure gaining market share thanks to a shortened travel and maybe improving profitability by a more intensive use of the rolling stocks if the maintenance costs are kept reasonable concerning rolling stocks as well as railway infrastructure. But that project would really reach the aims quoted above by keeping the number of paths unchanged. Now except at low speed the headway between two trains following each other at a constant speed is roughly proportional to the speed. It means that, if we keep unchanged the braking parameters, increasing the speed will decrease the capacity of a high speed line and hence reduce the revenues brought by that line.

It is why SNCF has undertaken on the last 12 months a study aiming at defining the conditions enabling to increase the speed from 300 km/h to 360 km/h whilst achieving the same headway. In other words, the aim is to be able to schedule trains running at 360 km/h three minutes apart, exactly as it is done today but at 300 km/h on most of the French high-speed lines.

This study thus gave an account of the current situation in matter of headway at 300 km/h but on a high-speed line which is not equipped of the last French version of TVM 430 system because this one had not been designed for a speed greater than 320 km/h yet. Therefore the hypothesis of a high-

IGT.SE-CA-JS-WCRR-20110215 1/10 Challenge E: Bringing the territories closer together at higher speeds speed line with European Control System Level 2 had been chosen to estimate technical headways expected at 360 km/h thanks to new trains. The current SNCF’s rolling stocks have not indeed been designed to operate at 360 km/h. Finally the gap between the last SNCF rolling stock configuration and those are potentially contemplated to run at 360 km/h had been highlighted too regarding both operating conditions and safety considerations.

2. METHODS

2.1 Railways Capacity background

Railways capacity is generally estimated through its maximal number of trains per hour that can be reasonably hosted in one hour for one direction, according to a timetable which is based on practical headways between two trains. Railway capacity or practical headway time basically depends on the succession of train path types, technical headways time and stability level whished. In this study SNCF focused on the technical headway time which is the minimum time ensuring that the second train can run safely without be perturbed by the first one in nominal situation. The track in particularly must seem clear from the driver’s point of view of the second train. From here, unless otherwise specified, headway term will tacitly refer to technical headway.

Headway time on a track section represents the time taken by the first train to run over the necessary headway distance from the critical point of this track section. The critical point can be defined as the place where the restrictive indication is about to be perceived but not seen by the driver of the second train. All things being equal except speed parameter and although running faster lets the train to cover a distance more rapidly, headway distance is at high speed roughly proportional to speed because of stopping distance. Headway distance indeed mainly depends on such parameters like cab signalling indications based on a stopping distance in first rate, distance from point to be protected to point targeted and system time in generally second rate. Block length has to be taken into account too because it has an influence over refresh rate of the first train position. Finally, the plain line headway time H [s] as a function of speed could be obtained through the formula below.

v L  L  d H(v)  t   T  2. v

With v [m/s] as speed, tΣ [s] as system time,  [m/s²] as service deceleration, L [m] as a length of the block where the first train is located, LT [m] as the length of the first train and d [m] as a length taking into account specificities of the signalling system detailed below. As a result the graph in the figure 1 presents as an example the hyperbola branch and then the minimum reach in a critical speed VC. Therefore headway time is stable above VC and unstable below VC.

Figure 1 – plain line headway time according to speed and stability issues

IGT.SE-CA-JS-WCRR-20110215 2/10 Challenge E: Bringing the territories closer together at higher speeds

Another topic which must normally be tackled is the stability issues of the timetable but it was out of the scope of this short study. It would indeed require a lot of simulations taking into account the variability of all the parameters of the problem. What could be understood in one simplistic way is for a timetable given, the decrease of technical headway time leads to an increase of the stability of the timetable. In a way, railways capacity is first linked to both railway infrastructure and rolling stock issues, and these notions are therefore explained below.

2.2 Railway infrastructure

We have assumed that the railway infrastructure on which this study had been achieved is not equipped of the national signalling system TVM 430 used in the most recent French high-speed lines. The signalling system ETCS L2 is not superimposed on this national signalling system as it is the case on the French high-speed line East European which to date the last high-speed line come into service in France. The following two paragraphs are going to put in highlights the differences between both signalling systems and to describe the high-speed line characteristics that had been set for this stuff.

2.2.1 Signalling systems

Both signalling systems TVM 430 and ETCS L2 are based on a cab signalling and a speed control. They are based too on the principle of the track-side detection of train occupancy and have the continuous transmission what is imply that the second train receives after a delay of transmission and treatment the information as soon as a block is released by the first one and not when it crosses information point as a trackside signal or a balise.

The principles linked to the cab signalling indications and the way to protect a point are however few different. So the way to calculate headway times changes from a signalling system to another. Cab signalling indications have an influence on the place where the driver perceives the first restrictive indication and on the speed on which the train is travelling during the stopping or slowing down sequence.

The stopping distance therefore depends on the signalling system considered. With TVM 430 signalling system, stopping distance is defined by a number of block sections with a minimal length according to gradient. This number of block sections depends obviously on the intermediate speeds indication displayed which have been defined in coherence with service brake deceleration required in order to achieve each speed transitions into a block. The first block section where appears the restrictive indication is the place where the driver is informed that the service braking has to be started at the latest at the end of that block. In case of non-respect of the supervised speed by the driver, the emergency braking is triggered but the stopping distance defined by those set of blocks could not in some case be sufficient to prevent the train from overshooting the protected point and it is why an overlap is added to this set of blocks. Therefore rolling stocks have to be compatible with this infrastructure from service brake deceleration and emergency brake deceleration point of view.

Things are quite different with ETCS L2 signalling system where stopping distance is calculated on board and based on the own rolling stock performances, and not the minimal performances imposed by the railway infrastructure. Therefore stopping distance does not depend on block section length. A “pre indication” – white indication – is shown to the driver to inform about a potential stopping or slowing sequence. The place where the driver has to start the service braking is located thanks to the “indication” which is a yellow indication. The places where the white or the yellow signalling indications are displayed into a block depend on the braking distance. Although there were some debates about which should be considered as the first restrictive indication, it is admitted that the pre indication would the first restrictive indication on what the headway is calculated. In addition there are not intermediate speeds to respect contrary to what is done in TVM 430, and the permitted speed can be known by the driver continuously. In France, a short overlap has been moreover imposed by the National Safety Authority on high-speed lines to add an extra margin in order to ensure the non- overshooting of the point to be protected.

IGT.SE-CA-JS-WCRR-20110215 3/10 Challenge E: Bringing the territories closer together at higher speeds

2.2.2 High-speed line characteristics and scenarios considered

On this study headway times have been calculated on a track section presenting constant gradients - 0‰ and 10‰ slope - and block sections with a constant length of 1 500 m (even in falling gradient) ; such a choice is possible as there is no implementation of a national signalling system. Ready to be crossed at 360 km/h in plain line, this high-speed line has no gradient on junctions. These junctions were crossed at 230 km/h if the route is toward a high-speed line section with the same signalling system or at 160 km/h rail if the route is toward the French rail network classic with trackside signals. A slow down scenario to 300 km/h without gradient had been tested too. These speed values are those which are widely used on the French high-speed lines. The figure 2 sums up the scenarios which had been considered.

SCENARIO N°1 Plain line at the train max speed -5% with a flat profile SCENARIO N°2 Plain line at the train max speed -5% with 10‰ slope SCENARIO N°3 Junction crossed at 230 km/h without gradient SCENARIO N°4 Junction crossed at 160 km/h without gradient SCENARIO N°5 Slow down from the train max speed -5% to 300 km/h without gradient

Figure 2 – scenarios considered in this study to calculate headways time with ETCS L2

In addition for each train with a max speed given, only some of the scenarios listed above are really determinant when it is about to design the timetable. Finally, the scenario N°5 is generally linked to a temporary speed limit especially on a very high-speed line. As a result this scenario was studied just to show what could be expected.

2.3 High-speed rail rolling stock design

All parameters useful to calculate headway distance vary obviously according to signalling system but also with braking deceleration performances based on some assessments linked to safety level, calculation method and operating conditions. Cab signalling TVM 430 is based on a specially built railway infrastructure compatible with the rolling stock having the worst braking decelerations performances, now backward compatibility has to be kept with the current rolling stocks. It is why in this section we will focus on the braking deceleration curves used in the cab signalling ETCS because it depends tacitly on the own rolling stock design, and ETCS will be necessarily deployed on new French high-speed lines.

The TGV POS whose top speed is 320 km/h and both “Next-Generation” TGV whose top speed is 360 km/h with new designs had been considered in this study. The new designs were based on a configuration well known by SNCF. They were indeed in particular 200 meters long and made up of 13 bogies as it is the case with the TGV POS. From here NG TGV term will refer to Next-Generation TGV.

2.3.1 Braking system types

High speed rail rolling stock can use some types of braking system in order to satisfy the requirements on which they are designed for. In this context, possible braking systems could be friction systems like electro pneumatic braking and electromagnetic braking or non friction systems like both and linear eddy current braking.

The braking systems used on the TGV POS are electro pneumatic braking and dynamic braking. On this train, dynamic braking relies on both regenerative and rheostatic braking. As regard to new trains to study, we opted for these both non friction braking systems when thinking about two rolling stock designs which would potentially achieve the headway. But one of those used an extra non friction braking system based on eddy currents too in order to assess the advantages provided by such a technology choice.

IGT.SE-CA-JS-WCRR-20110215 4/10 Challenge E: Bringing the territories closer together at higher speeds

It is necessary to recall the characteristics of these non friction braking systems to understand later in this article how ETCS braking curves are designed. Regenerative braking is transforming kinetic energy into electrical energy using motors as generator during the braking in case of emergency braking, and then providing that energy to the railway power supply system. The working of regenerative braking requires therefore an high availability rate of the power supply system. It is why rheostatic braking has to be implemented when the availability rate of a railway electrical network, which is linked to technological choices and power supply components of each railway lines, is not considered high enough regarding safety issues. Rheostatic braking indeed does not depend on power supply system since electrical energy is dissipated as heat in brake grid resistors. The disadvantage of such a system however is the required space by the fans used to cool it. Linear eddy currents braking, which were thought by the French physicist Foucault, is not linked with the power supply system too. This braking technology implemented on some bogies consists in adding coils which generate a variable magnetic field in order to produce eddy currents on the rails. Now, both eddy current on the rail and magnetic fields brought by the train create a force. The horizontal force component is used to slow down the train whereas the vertical force component attracts the track to the train especially at low speed. In this study linear eddy currents would in particular not be considered as enabled at a speed lower than 200 km/h. The main disadvantages of this technology are thus the warming of the rail, the attractive force and the mass of the system.

2.3.2 High-speed train concepts

The NG TGV concepts had been determined to fulfil national and European standards about braking performances and to provide at least the same headway with the signalling system ETCS L2 at 360 km/h in plain line without relief that it could be obtained at 300 km/h with the signalling system TVM 430.

The TGV POS is a train 200 meters long which is made up of 13 bogies including 4 powered ones (PB), the latter each have a rheostat (Rh). As regard the considered NG TGV, first one has an extra powered bogie without rheostat, and 4 of remaining 8 others non-powered bogies (NPB) have linear eddy currents brakes (LECB). In comparison with the TGV POS, the other considered NG TGV has not linear eddy currents brakes but two extra powered bogies with each a rheostat. The whole of concepts considered in this study are summed up in the figure 3.

DESIGNATION OF ROLLING STOCK CONCEPTS TOP SPEED TGV POS 4PB 9NPB 4Rh 320 km/h NG TGV with Linear Eddy Currents Brakes 5PB 8NPB 4Rh 4LECB 360 km/h NG TGV with six Powered Bogies 6PB 7NPB 6Rh 360 km/h

Figure 3 – rolling stock architectures considered in this study

2.3.3 ETCS braking curves

Safety and indications provided by the cab signalling are based on braking curves which are determined from the proper rolling stock performances according to the gradient. Among ETCS curves, the Emergency Brake Deceleration curve (EBD), the Emergency Brake Intervention curve (EBI) and the Guidance curve (GUI) are essentially taken into account for SNCF’s TGV trains.

The EBD curve is the minimum deceleration which the train will achieve with the very high level of reliability, required for safety, when the emergency brake system is activated. The deceleration values for a range speed given are provided according to a chance equal to 10-9 to overshoot the stop point targeted in a day taking into account the driver’s contribution. For a safety level given, the deceleration values can be different from a calculation method to another. From the nominal deceleration values that the train is able to provide considering its characteristics, SNCF had worked with two different methods to determine safe deceleration values. Those are the combinatory method and Monte-Carlo method. The former is not so much used, whereas the latter must be the most precise and so provide higher safe deceleration values. In any case it was necessary to take into

IGT.SE-CA-JS-WCRR-20110215 5/10 Challenge E: Bringing the territories closer together at higher speeds account the operating condition of various braking system. For instance, studies about availability rate of the power supply system of the French high-speed lines and solutions to improve it had not been realized. It is why the EBD curves of the TGV addressed on this study only referred to rheostatic braking and if need be linear eddy currents braking, and could not take into account the possibility to use regenerative braking safely during an emergency braking.

The EBI is the curve which ensures that the emergency braking is triggered at time in order to prevent the train from passing the stop point targeted. This curve is deduced from EBD curve, takes into account in particular some parameters like traction cut time, safe brake build up time, and uncertainty in speed and position.

Taking into account the gradient profile of the rail track, the permitted speed is deduced in each speed range from the most restrictive between a curve which is deduced from a translation time of the EBI curve – the Max Permitted Speed that the system could allow (MPS Curve), and a guidance curve. The GUI curve lets to fit a service braking considering the ease of driving and the wear on braking components issues. For instance, the GUI curve chosen by a railway could be based on an Electric Service Braking (ESB GUI curve) or on an Electric Pneumatic Service Braking (EPSB GUI curve).

All the ETCS braking curves addressed in this article are shown in the figure 4.

Figure 4 – ETCS braking curves: EBD, EBI, MPS, EPSB GUI and ESB GUI

2.4 Contents of the study

This study was divided into three parts. The first part was to measure the current headway times obtained at 300 km/h and at 320 km/h with the TGV POS for further comparisons. The second part of the study had to make indeed a significant comparison in order to measure the benefits of the new train concepts all other things being equal at the relevant speed therefore at the top speed of the TGV POS. Finally the third part let to check how the NG TGV considered could satisfy the headway criterion especially at 300 km/h. The figure 5 shows all the trains examined, and where the train N°1 was the reference at 300 km/h and the train N°2 was the reference at 320 km/h in the study.

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ARCHITECTURE EBD CURVE METHOD MAX SPEED TRAIN N°1 4PB 9NPB 4Rh Combinatory method 300 km/h 1st PART TRAIN N°2 4PB 9NPB 4Rh Combinatory method 320 km/h TRAIN N°3 4PB 9NPB 4Rh Monte-Carlo method 320 km/h 2nd PART TRAIN N°4 5PB 8NPB 4Rh 4LECB Monte-Carlo method 320 km/h TRAIN N°5 6PB 7NPB 6Rh Monte-Carlo method 320 km/h TRAIN N°6 5PB 8NPB 4Rh 4LECB Monte-Carlo method 360 km/h 3rd PART TRAIN N°7 6PB 7NPB 6Rh Monte-Carlo method 360 km/h

Figure 5 – trains considered in this study

As regard the first restrictive indication debate we had the opportunity thanks to these calculations to quantify the improvement of the performance by referring to “indication” instead of “pre indication” in the calculations. In addition, an Electric Service Braking GUI curve and an Electric Pneumatic Service Braking GUI curve had been assessed for each NG TGV. The former used only dynamic braking, and linear eddy currents braking when the trains get it whereas the latter in addition used pneumatic braking.

3. RESULTS

As expected the study shown that the worst headway time was obtained with the scenario N°4 for each train, and that on the whole it was the most difficult to satisfy the headway criterion with this scenario at 360 km/h. So headway times obtained with the scenario N°4 are the most critical and it is why the paper will sometimes focus on this scenario. The results of the study are summed up below.

3.1 A drop in headway times using the ETCS “indication” instead of the “pre indication”

The drop in headway times by putting the ETCS “indication” as the first restrictive indication instead of the ETCS “pre-indication” was measured, as the figure 6 shows it. It depended on the scenario and the train considered. As regard to the TGV POS the increase of performance varied from 10% to 14 % depending on scenarios. Without considering the scenario N°5, improvements with regard to the new trains were each other the same for the scenario N°1, N°2 and N°3 and were about between 12% and 13%. On the scenario N°4 the drop in headway times is about to 7% or 8%.

SCENARIO N°1 SCENARIO N°2 SCENARIO N°3 SCENARIO N°4 SCENARIO N°5

indication 14 % BETTER 12 % BETTER 13 % BETTER 10 % BETTER TRAIN N°1 pre indication Reference Reference Reference Reference Reference indication 13 % BETTER 13 % BETTER 12 % BETTER 8 % BETTER 3 % BETTER TRAIN N°6 pre indication Reference Reference Reference Reference Reference indication 13 % BETTER 13 % BETTER 12 % BETTER 7 % BETTER 7 % BETTER TRAIN N°7 pre indication Reference Reference Reference Reference Reference

Figure 6 – Estimation of the use of ETCS “indication” to calculate headway times for each train

From here, the comments made on values linked to headway times will tacitly refer to those based on the “pre indication” because it is so far the preferred option. Figures linked to the “indication” will be displayed just for information.

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3.2 A drop in headway times with the NG TGV at 320 km/h in comparison with the TGV POS

The drop in headway times thanks to the new trains using the ESB GUI curve was measured, as the figure 7 shows it. The NG TGV with linear eddy currents brakes provided at least headway times 17 % shorter than those obtained from the TGV POS. The NG TGV with six powered bogies let to have headway times at least 12 % shorter than those obtained with the latter. We can notice that the relative improvement noted with the scenario of the high-speed line exit was not as strong as those noted with the scenario of the plain line without gradient.

SCENARIO N°1 SCENARIO N°4

indication Reference Reference TRAIN N°3 pre indication Reference Reference indication 19 % BETTER 18 % BETTER TRAIN N°4 pre indication 20 % BETTER 17 % BETTER indication 13 % BETTER 11 % BETTER TRAIN N°5 pre indication 13 % BETTER 12 % BETTER

Figure 7 – Headway times improvements thanks to the new trains all other things being equal

3.3 A drop in headway times using the Electric Pneumatic Service Braking at 360 km/h

The drop in headway times by using the EPSB instead of the ESB had been noted, as the figure 8 shows it. For instance considering the scenario N°4, the headway time with the NG TGV with six powered bogies is 7% shorter whereas the one as regard the NG TGV with linear eddy currents brakes is 5% shorter.

SCENARIO N°1 SCENARIO N°4

Electric GUI Electric Pneumatic GUI Electric GUI Electric Pneumatic GUI indication Reference 5 % BETTER Reference 6 % BETTER TRAIN N°6 pre indication Reference 6 % BETTER Reference 5 % BETTER indication Reference 8 % BETTER Reference 9 % BETTER TRAIN N°7 pre indication Reference 9 % BETTER Reference 7 % BETTER

Figure 8 – Estimation of the drop in headway times by using an EPSB GUI curve

3.4 Achieving the same headway whilst increasing the speed from 320 km/h to 360 km/h

As the figure 9 shows it, the NG TGV with linear eddy currents brakes and an ESB GUI curve clearly let to have headway times at 360 km/h shorter than those existing at 320 km/h. The same had been practically found for the NG TGV with six powered bogies.

SCENARIO N°1 SCENARIO N°2 SCENARIO N°3 SCENARIO N°4 SCENARIO N°5

indication Reference Reference Reference Reference Reference TRAIN N°2 pre indication Reference Reference Reference Reference Reference indication 13 % BETTER 18 % BETTER 8 % BETTER 7 % BETTER 2 % BETTER TRAIN N°6 pre indication 14 % BETTER 19 % BETTER 10 % BETTER 8 % BETTER 7 % BETTER indication 5 % BETTER 8 % BETTER AS GOOD AS -2 % WORSE -3 % WORSE TRAIN N°7 pre indication 5 % BETTER 8 % BETTER AS GOOD AS AS GOOD AS -2 % WORSE

Figure 9 – Checking if the headway criterion at 320 km/h is fulfilled with an ESB GUI curve

IGT.SE-CA-JS-WCRR-20110215 8/10 Challenge E: Bringing the territories closer together at higher speeds

3.5 Achieving the same headway whilst increasing the speed from 300 km/h to 360 km/h

As the figure 10 shows it, the NG TGV with linear eddy currents brakes and an ESB GUI curve let to achieve at 360 km/h the same headway provided by the TGV POS at 300 km/h. The same had not been found for the NG TGV with six powered bogies.

SCENARIO N°1 SCENARIO N°2 SCENARIO N°3 SCENARIO N°4 SCENARIO N°5

indication Reference Reference Reference Reference TRAIN N°1 pre indication Reference Reference Reference Reference indication 8 % BETTER 15 % BETTER AS GOOD AS -2 % WORSE -12 % WORSE TRAIN N°6 pre indication 9 % BETTER 14 % BETTER 2 % BETTER 1 % BETTER AS GOOD AS indication AS GOOD AS 4 % BETTER -10 % WORSE -12 % WORSE -18 % WORSE TRAIN N°7 pre indication AS GOOD AS 3 % BETTER -8 % WORSE -8 % WORSE -9 % WORSE

Figure 10 – Checking if the headway criterion at 300 km/h is fulfilled with an ESB GUI curve

As the figure 11 shows it, the NG TGV with linear eddy currents brakes and an EPSB GUI curve let obviously to achieve at 360 km/h the same headway provided by the TGV POS at 300 km/h. The same had been practically found for the NG TGV with six powered bogies.

SCENARIO N°4

Electric GUI Electric Pneumatic GUI indication Reference Reference TRAIN N°1 pre indication Reference Reference indication -2 % WORSE 4 % BETTER TRAIN N°6 pre indication 1 % BETTER 6 % BETTER indication -12 % WORSE -2 % WORSE TRAIN N°7 pre indication -8 % WORSE AS GOOD AS

Figure 11 – Checking if the headway criterion at 300 km/h is fulfilled with an EPSB GUI curve

4. DISCUSSION

First the results shown that, from a speed given, stopping distance in complex scenarios like junctions with a slow down had not the same importance as those seen with a scenario of two trains following each other at the same speed in a plain line. Interlocking system time or/and train occupancy time of the first train running at low speed have indeed more influence on the technical headway times.

As regard to the new trains studied, the performance of the NG TGV with linear eddy current brakes was clearly greater than the NG TGV with six powered bogies one. The gap was more important at very high-speed because linear eddy currents brakes were only available at a speed greater than 200 km/h.

Moreover, the gap between the ESB and the EPSB is greater with the NG TGV with six powered bogies than the gap found with the other. Indeed, for each train the working hypothesis adopted lead to fit the EPSB curve to the MPS curve. Now, the NG TGV with linear eddy currents braking can use it both to its safe emergency braking and to its service braking.

In addition, the emergency braking was likely to become the restrictive point if there is a will to improve the deceleration value of the EPSB, or with the same EPSB to make the driving easier to prevent the driver from passing the warning limit or triggering the emergency braking when passing the EBI curve.

IGT.SE-CA-JS-WCRR-20110215 9/10 Challenge E: Bringing the territories closer together at higher speeds

5. CONCLUSION AND FUTURE WORK

The aim of this study was to compare performances of new rolling stock architectures which could be reasonably contemplated to operate at 360 km/h to those currently obtained at 300 km/h in France. Considering TGV POS operating on a railway infrastructure with ETCS L2 cab signalling system and using the ESB GUI curve as the reference situation, some conclusions can be drawn and are exposed below.

The train architecture having in particularly linear eddy current brakes would allow achieving at least the headway time obtained in the reference situation only using the ESB GUI curve on the whole scenarios considered. A headway time smaller than three minutes was moreover reached if the EPSB GUI curve is implemented instead of the ESB GUI curve. On the other hand the one which had six powered bogies without linear eddy current brakes was not compliant with the headway time goal to achieve by using the ESB GUI curve. It was however interesting to notice that the headway time requirements to achieve considering the speed of 320 km/h could be fulfilled at 360 km/h with this GUI curve. This train architecture would in fact allow achieving at least the same headway time that the reference situation on the whole tackled scenarios provided that the EPSB GUI curve is used. However so far it has not been proved that a train is easy to drive with an EPSB GUI and further studies on this issue have to be done.

Thus increasing the speed of the trains from 300 km/h to 360 km/h without falling capacity on high- speed lines is a goal that can be reasonably reached assuming that constraints generated by using eddy current brakes can be managed or the driving ease due to the electric pneumatic guidance is considered acceptable. It is why we will go into both subjects in greater depth in a next step.

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