computers in railways vii, c.a. brebbia j.allan, r.j. … · figure 3: lay-out of firenze node,...

Introduction of a new high speed line in a high

density traffic area: a simulation exercise

G. Astengo*, G. Cosulich*, D. Marzullo

*SciroS.r.L, Italy

Abstract

The introduction of a new high speed line in an important railway area includinga main station has a significant impact on the whole railway area. A soundestimation of the consequent modification of the traffic pattern is thereforerequired, together with the study of the new track layout of the area. Manydifferent solutions can be considered, for the traffic pattern, the track plan andthe traffic control system. The optimised solution choice involves a set ofcomputer-based simulation models of the variables of the problem (track layout,rolling stock, signalling, traffic density) and the costs and benefits evaluation.The paper describes the study carried out for the area of Florence, where twohigh speed lines converge together with other seven ordinary speed lines,carrying a dense traffic of long distance passenger trains, commuter trains,freight trains. The area includes the main station of Florence and a number ofminor stations. The study includes:

a model of the track layout of the areaa set of proposed solutions of the traffic timetable for the whole areathe model of the different types of rolling stockthe model of the signalling systemthe simulation of the traffic alternative scenariosthe simulation of the utilisation of the platform tracks in the main stationthe evaluation of the effect of perturbations on the traffic capacitythe evaluation of the results.

The details of the area layout and expected traffic are presented, together withexamples of graphic timetables, track occupation diagrams, traffic capacityevaluation, perturbation effects.

Computers in Railways VII, C.A. Brebbia J.Allan, R.J. Hill, G. Sciutto & S. Sone (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-826-0

212

1 Introduction

Computers in Railways VII

The town of Firenze (Florence) is an important node of the Italian railwaynetwork, where the lines to/from Bologna-Milano, Roma, Pisa converge,together with other secondary lines.

In the early 90s a new high speed line to Roma entered in operation, whilearound the year 2006 or 2007 another high speed line to Bologna is scheduled tobe completed. Furthermore, two secondary lines and other additional tracks willbe added in the area, in order to withstand the expected traffic increase.

The map of the area (fig. 1) gives a complete view of the existing and futurelines: two ordinary speed lines to Bologna, the future high speed line to Bologna,two double track ordinary speed lines to Pisa, a double track ordinary speed lineto Roma, a high speed line to Roma, a couple of single track secondary lines, aset of connections between the main station of Firenze Santa Maria Novella andthe other stations of the Firenze area.

NODO 01 MRENZESCCUAKOSGRVKBO REGIONALS

SERYI3O METROPOUTANO

BbZ-*/ ( .M>A04>* IWM**** I ;**,Kx*I M*

Fig. 1

The schematic layout of fig. 2 shows the details of the railway connections of thearea foreseen on the year 2003, i. e. before the introduction of the new highspeed line to Bologna. The main terminus station of Firenze SMN (Santa MariaNovella) has 18 tracks and is linked by four tracks to Firenze Rifredi - FirenzeCastello and two other tracks to Bivio Pellegrino and Firenze Campo Marte.Pontassieve is the entrance station of the ordinary speed line to Roma, ValdarnoNord is the entrance station of the high speed line to Roma, Firenze Cascine and


Computers in Railways VII 213

Pistoia are the entrance stations of the two lines to Pisa, Pistoia and Vaiano arethe entrance stations of the two existing lines to Bologna.

I Pistoia I I Vaiano j—2-Montale j

Junction StationIntermediate Station

Stop StationSingle-track line

Double-track lineArc n of the graph

1

D

O

I Pontassieve |

Figure 2: Lay-out of Firenze node, year 2003


214 Computers in Railways VII

CalenzanoI DP | |CampiBisenzio| ——

Junction StationIntermediate Station

Stop StationSingle-track line

Double-track lineArc n of the graph

1 10o

n >•

Figure 3: Lay-out of Firenze node, year 2008

The schematic layout of fig. 3 shows the scenario foreseen on the year2008, when the new high speed line to/from Bologna will be in operation via theentrance station of Firenze Castello. A new underground line will be added fromFirenze Castello to Bivio Rovezzano - Valdarno Nord in order to have a directlink between the two high speed lines from Bologna and Roma. Some minorstations in the town area and a new line to Campi Bisenzio will also be added.

The 2008 scenario represents the final situation of the Firenze area after thecompletion of the restructuring plan, while the 2003 scenario already includessome significant improvements on the present situation (year 1999).



It was therefore required by the Italian Railways to carry out a simulationexercise on both scenarios, in order to evaluate the traffic potentiality in the areaand the feasibility of new local and regional services, taking into account theexpected traffic increase in the high speed connection Milano - Bologna -Firenze - Roma.

2 The simulation tool

To comply with the above requirements, a modular simulation tool wasemployed, able to provide a set of functions, such as:a) simulation of the network layout for both scenarios (2003 and 2008), as

shown in fig. 2 and 3, including stations, tracks, switches, gradients, speedrestrictions

b) simulation of the signalling systems throughout the area, includinginterlocking, coded current automatic block, ERTMS with Eurobalisetransponders, axle counters on the secondary lines

c) simulation of train parameters (traction equipment, number of cars, maxspeed, braking equipment, weight, ...) for all types of trains operating in thearea (high speed trains, long distance passenger trains, commuter trains,freight trains, ...)

d) simulation of train circulation throughout the area, using the typicalmovement equations (traction and braking) and the network layout data

e) provision of both numeric and graphic output, including time-distance traindiagrams (graphic timetable) and information display about train delays

f) capability of changing the value of the system variables, in order to optimisethe solutions and to evaluate the consequences of possible trafficperturbations.

Simulator structure

Figure 4 - The simulator structure


2\(\ Computers in Railways VII

The structure of the simulation tool is shown in fig. 4: three sets of inputs(network layout, timetable, train data) are introduced in the five basic simulatormodules, which provide the outputs such as the graphic timetable, the pattern oftrain position over the area, the power requirements vs. time, etc.

The simulation programme has been implemented using C++ language andObject Oriented Analysis and Design technique, building a modular structure ofthe tool. The software is allocated in a set of independent modules, each onecontaining the functions and the data base concerning a specific entity. Eachsystem component is described by means of a set of standard parameter values,which can be stored in the memory and subsequently modified and re-used inother simulations.

3 The simulation methodology

The methodology of simulation has been developed through a sequence of steps,from the definition of the input data to the traffic simulation and timetableoptimisation; furthermore additional simulations have been carried out toevaluate the consequences of traffic perturbations.

3.1 Definition of the network model

The layout of the network area is represented by an oriented graph; each node isan entrance location of the network or an internal location where more than twolines converge (e.g. a junction); each arc (or edge) is the portion of line linkingtwo nodes and is characterised by the number of tracks, the gradient, the curves,the allowed speed values, the wayside signals position, the type of signalling; anarc can include one or more locations (=stations). The Firenze network graph(scenario 2003) includes 18 nodes and 24 arcs; 2 arcs have one track and areoperated by axle-counter block, whilst the other 22 have two tracks and areoperated by automatic block. The graph for the scenario 2008 includes 20 nodesand 27 arcs (2 single-track, 25 double track).

3.2 Definition of the trains

For each train the list of cars, the locomotive data, the traction curve, theacceleration/deceleration values, the max speed value, the mechanical resistance,the length and the weight are defined.

3.3 Definition of route and time

Each route is defined by a sequence of arcs and can be associated to a list oftrains travelling on the route; taking into account the train speed, the stops insidethe route, the dwelling times, the time allowance for delays, the simulatorcalculates the time-distance diagram of each train; consequently a capacity valuecan be defined, in terms of max number of trains of certain type which can travel



each hour on each route, taking into account the train speed, the stops inside theroute, the dwelling times, the time allowance for delays.

3.4 Building a reference timetable

A first tentative timetable, including all trains scheduled in the operationprogramme, is built on the basis of the above data definition. Afterwards a set ofiterative simulations is carried out, aiming to minimise the delays and theinterference between trains. The final result is a "reference timetable", withoutdelays or circulation problems.

3.5 Simulating the traffic perturbations

An additional set of simulation exercises allows to evaluate the consequences oftraffic perturbations, originating from delays on train departure or arrival time.Other simulations can concern other kind of perturbations, such as the failure ofa train on line, the unavailability of a track for maintenance or other reasons, thespeed restriction for works in progress, etc.

3.6 Definition of the station layout model

The representation of the layout of a station, in particular the main station ofFirenze SMN (Santa Maria Novella), includes the detailed definition of theroutes, the track circuits, the signal position, the station tracks.

3.7 Simulation of the traffic inside the main station

The reference timetable under para 3.4 can be checked through a simulation ofthe traffic inside the main terminus station of Firenze SMN, in order to evaluatethe compatibility of the timetable with the station layout and to optimise theutilisation of the station tracks.

4 The simulation work

The aim of the simulation work was to evaluate the traffic capacity of the Firenzearea network, checking the compatibility of the network configuration for theyears 2003 and 2008 (fig. 2 and 3) with the corresponding traffic flowestimations.

4.1 Identifying the traffic flows

For each scenario (2003, 2008) a table of typical routes has been provided, wherea route means the link between two points of the network for a certain type oftrain, i.e. with a given speed profile and following a given route pattern (non-stopor stopping at certain intermediate locations). Each route is characterised by a



sequence of arcs of the graph, a type of train, a type of service (a train every ....minutes). The fig 5 shows an example of the table of typical routes for thescenario 2003.

123"456789W111213141516171819202122232425262728293031

Vaiano - Fi SMN - Vald. NordVaiano - Fi SMN - Vald. Nord~ " ~ Vaiano-Fi SMN

~ Vaiano - Fi SMNVaiano- Fi Campo Marte

Pistoia Fi SMNPistoia Fi SMNPistoia Fi SMN

Fi. Cascine Fi SMN

1/3/5/7/9/12/14/15/171/3/5/7/9/12/14/15/17

1/3/5/7/91/3/5/7/91/3/5/7/112/4/6/8/92/4/6/8/92/4/6/8/922/20/10

Fi. Cascine Fi SMNFi. Cascine Fi'SMNVald. Nord - VaianoVald. Nord - VaianoPontassieve - PistoiaPontassieve - Pistoia

Vald. Nord - Fi SMN- VaianoVald. Nord - Fi SMN- Vaiano

FfSMN Vaiano"Valid. Nord - Pistoia

Fi SMN - PistoiaFi SMN - CascineFi SMN - Cascine

Valdarno Nord - Firenze SMNPontassieve - Fi SMNPontassieve - Fi SMNFi SMN Vald". NordFf SMN Vald. NordPi SMN -PontassieveFi SMN - PontassieveInizio Faenza - Fi SMNFi SMN - Inizio Faenza

* 2 22/20/10"-17M5M1-7/-57-3/-1-17/-15/-11-7/-5/-3/-1-18/-16/-11/-8/-6/-4/-2-18/-16/-11/-8/-6/-4/-2

-17/-1 5/- 1 4/- 1 2A9/-7/-5/-3/- 1- 1 II- 1 5/4 4/- 1 2/-9/-7/-5/-3/- 1

-9/-7/-5/-3/-r-17/-i5/-l"l7-8A6/-4/-2

_9/.g/_6/_4/-2-10/-20/-22-10/-20/-22

-17/-16/-14/-12-18/-16/-14/-12-18/-16/-14/-1212/14/16/1712/14/16/17

* 12/14/16/18" 12/14/16/18

-13/-1212/13

High SpeedOrd. Speed

" Ord SpeedRegional 2Regional 2Ord. SpeedRegional 2MetropolitanOrd.jSpeedRegional 2MetropolitanHighspeed'Ord. SpeedRegional 2MetropolitanHigh SpeedOrd. SpeedOrd.jSpeed

" Ord. "SpeedOrd. SpeedOrd. SpeedRegional 2Ord. SpeedRegional 2MetropolitanHigh SpeedOrd. SpeedRegional 2MetropolitanRegional 1Regional 1

60'3(T60'120'120'120'30'60'30'20'120'120'60'30'30'60'30'120'1260'30'30'30'15'15'120'"630'120'30'30'

Fig. 5 - Table of typical routes

This table allows to build the standard space-time diagram to be associated toeach typical route.

4.2 Building the space-time diagram

Knowing the list of the scheduled trains for the whole network, it is possible tobuild a set of space-time diagrams, one for each typical link in the area.



Figure 6 Figure 7

The figures 6 and 7 show two examples of diagram, the fig. 6 concerns the uptrack from Valdarno Nord (high speed from Rome) to Firenze Rifredi, the fig. 7the up track from Pontassieve (ordinary speed from Roma) to Firenze SMN,where on the section Firenze SMN - Firenze Campo Marte the long distancetrains from Rome run together with local trains to Faenza and high speed trainsto Roma.

4.3 The station track occupation chart

Another output of the simulation work is the track occupation chart in theterminus station of Firenze SMN. The figure 8 shows the section covering thetime window from 6:00 to 10:00 hrs. Each train is represented by a rectangle,where the central portion is the track occupation time and the side portionsrepresent the duration of entrance and exit routes. The two train numbers of eachrectangle correspond to incoming and outcoming trains respectively.

4.4 Evaluating the consequence of a delayed train

Several simulation exercises have been carried out introducing a delay (10' - 15'- 20') of a single train or a fleet of trains running on the same route, in order toevaluate the effect on the other train diagrams, the chance of recovering the delay(or a portion of it) and the modifications of the train occupation charts of theFirenze SMN terminus station.

5 Results and conclusions

The simulation work has allowed to confirm the feasibility of the traffic flowestimations for both scenarios 2003 and 2008, in particular for the compatibilityof the long distance high speed train with ordinary speed train and regional traintraffic. Furthermore the operation of fleets of trains running at constant time



intervals on each route was confirmed, checking both the capacity of the lines

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and the train occupation chart of Firenze SMN station. The simulation of thetraffic perturbations (delay of a train or a fleet of trains) has allowed to evaluatethe interference with the other train timetables and in certain cases the possibilityof recovering a portion of the delay.Other useful indications concerned the modifications to be introduced in thespecifications of the new interlocking of Firenze SMN in order to comply withthe response time of certain route controls.

References

[I] G. Astengo, A. Castagnola, G. Cosulich, A new approach to modelsignalling systems on railway networks. Comprail 98 (Computer in RailwaysVI), p. 1077, Lisbon 1998.[2] G. Astengo, A. Castagnola, G. Cosulich, A simulation tool for thecomparison of rail network layout and signalling system alternative solutions.ASPECT 99 Proceedings, p. 160, London 1999.


computers in railways vii, c.a. brebbia j.allan, r.j. … · figure 3: lay-out of firenze node,...

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