1193_1199_ramunas_gailiene_podagelis

7/29/2019 1193_1199_Ramunas_Gailiene_Podagelis

1/7

ENVIRONMENTAL ENGINEERING

The 8th International ConferenceMay 1920, 2011, Vilnius, LithuaniaSelected papers

ISSN 2029-7106print / ISSN 2029-7092 online

ISBN 978-9955-28-829-9 (3 Volume)

ISBN 978-9955-28-827-5 (3 Volumes)

http://enviro.vgtu.lt

Vilnius Gediminas Technical University, 2011

1193

INCREMENT OF RAILWAY LINE CAPACITY

Vaidas Ramunas1, Inesa Gailiene

2, Igoris Podagelis

3

1, 2, 3Vilnius Gediminas technical university, Saultekio ave.11, LT-10223 Vilnius, Lithuania.

E-mail:[email protected]

Abstract. As amount of transportation increases capacity in some railway infrastructure places becomes insufficient.Usually increment of number of tracks in all or part of an overloaded line seems the most simple and clear solution.However investments into infrastructure are very large and expansion of infrastructure in populous territories may beimpossible. Therefore all means enabling limitation or avoidance of infrastructure development or reconstructionhave to be discussed.The main parameter influencing railway line capacity is difference in train speeds. Increasing the difference betweenthe highest and the lowest train speed, feasible line capacity decreases. Reduction of the difference between trainspeeds enables increment of railway line capacity without changing infrastructure.A research estimating variables that determine commercial speed of trains and their importance is presented in thearticle. The commercial speed of trains depends on rolling stock traction and characteristics of breaking system, stop-page duration and some traffic control conditions. To decrease the difference between the train speeds the speed ofthe slowest trains has to be increased but the speed of the high speed trains must not be decreased. The freight trainsand the passenger trains that stop in the intermediate stations very often are the slowest ones in the mixed traffic rail-way lines. Influence of different variables is evaluated using sensitivity analysis thus estimating potential increase incapacity.In the research examples of AB Lietuvos geleinkeliai (SC Lithuanian railways) infrastructure are used. After

obtaining the results actions for increment of district capacity are suggested, without changing infrastructure parame-ters.The methodology assumes that the railway system consists of three main components: infrastructure, rolling stockand organizational traffic control means. When optimizing the railway transport system, interaction of the three com-ponents must be considered.

Keywords:railway infrastructure, line capacity, organizational means, train speed.

1. Introduction

As transportation demand increases most of the Europeanrailways meet the problem of insufficient line capacity.

Railway transport is safer, friendlier to environmentand more effective than the road transport (Adamko andKlima 2008; Bureika 2008; Dailydka et al. 2008; Lata2008; Lingaitis and Pukalskas 2008a, 2008b; 1986). However railway infrastructure needs hugeinvestments (Jaranien 2009; Maskelinait et al.2009; Lalive and Schmutzler 2008; Morkvnas et al.2008; Susnien and Jurkauskas 2008; elih et al. 2008;virblis and Zinkeviit 2008; Butkeviius 2007, 2008;Vasilis Vasiliauskas and Barysien 2008; Tolli and Lav-ing 2007; Su et al. 2006; 2006).

Increasing fuel prices, crowded roads and streets,environmental problems, increasing prices of public

transport enhance demand of passenger and freight trains(Butkeviius 2009). In the populous territories wheretransportation is insufficient, the line capacity is insuffi-

cient as well. Therefore the capacity becomes insufficientin the main lines that connect separate urbanized territo-ries too.

Usually the easiest way is chosen to increase the line

capacity, i.e. one more track is built in the lines or dis-tricts with insufficient capacity parameters. However it isexpensive solution and sometimes it is even impossible inpopulous territories. Therefore it should be discussed howtrain traffic in the existing infrastructure should be in-creased, intensifying operation and having limited re-sources. (Harrod 2007).

Train speed difference is the variable that has thegreatest influence on the line capacity. Having a possibil-ity to equalize (homogenize) the train speeds, much big-ger capacities could be gained. In the long districts dec-rement of high speed train speeds is ineffective and un-economic. Therefore increment of low speed train speeds

thus reducing the difference between the train speedswould be much more logic solution (Dessouky et al.2010). The freight trains and the passenger trains that


2/7

1194

stop in the intermediate stations very often are the slowestones in the mixed traffic railway lines Speed of thesetrains depends on their traction and stopping characteris-tics, traffic control systems/ways and other restrictionscaused by infrastructure (Buri and Tzieropoulos 2009).

Analysis described in the article is based on the ex-

amples of SC Lithuanian Railways infrastructure. Real-istic examples have been used to show that the line ca-pacity can be increased realizing exact technical or run-ning solutions.

2. Estimation of the capacity

Usually capacity is described as a number of trainspassing the district in some time. However the capacitycan not be expressed as exact value calculated accordingto a formula when railway network is concerned. Net-work capacity highly depends on the traffic schedule andtraffic consistence. Different schedules create different

network capacity. Every schedule requires different in-vestments into infrastructure (Harrod 2007; Abril et al.2007). Residual (reserve) capacity variation is subject tothe traffic consistency (e.g. mixed passenger and freighttrain traffic) (Landex 2008).

2.1. Line capacity in homogeneous traffic

It is not difficult to estimate the capacity in a linewhere the train speeds and stopping characteristics areidentical. Train routs in the diagram are homogeneous. Insuch case the capacity is inversely proportional to mini-mal interval (Abril et al. 2007). (A time span when two

trains pass straight one after another) (Fig 1.).

Fig 1. Line capacity in homogeneous traffic

If intermediate station has the only track to acceptthe train, common line capacity is reduced because of thestation capacity: coming trains can not be taken in untilthe former train leaves. Stopping time and especially timewhen passengers take a train are the factors that have thegreatest influence for estimation of minimal interval (Atime span when two trains pass straight one after another)

(SC Lithuanian Railways 2007).Generally it is discussed about totality of actions thatincrease the line capacities, until additional restrictions in

the terminal district stations (last stations of train rout)caused by the network performance emerge.

2.2. Line capacity in the mixed traffic

Mixed traffic with trains of different categories, hav-ing different stopping characteristics is the most commonin many lines. As speeds are not the same and times inthe train schedules are not homogenous the line capacityis influenced by two more factors (Dessouky et al. 2010;Harrod 2007): distance between contiguous stationswhere faster train can overtake the slower ones;train driv-ing order, i.e. order of routs in a district.

It is impossible to calculate track capacity using oneformula. In order to optimize the track capacity it is nec-essary to create a diagram. In figure 2 two different lay-outs of routs in the same district are presented. It is notedthat absolutely different capacities are obtained.

Fig 2. Line capacity in the mixed traffic

Therefore, if the stopping time of the slower train isincreased and the faster train overtakes it, the line capac-ity is increased. However service quality of the slowertrain decreases. Such solution is usually used for thefreight trains, but has to be avoided for the passengerones. Even in the very good railway lines stopping timeof the slow train is not less than 5-6 minutes. It markedlydecreases service quality and commercial usefulness(profitability).

2.3. Increment of the capacity increasing speeds of the

slowest trains

Train routes become very close in a mixed trafficwhen a train enters or leaves a station where the fastertrain overtakes the slower one. The maximum capacity isreached when the train routs are separated by the timeintervals equal to a time span when two trains passstraight one after another. This time span is also regulatedin the safety requirements. (Abril et al. 2007; Buri andTzieropoulos 2009; Noordeen 1996).

Speed increment of the slowest trains allows trainsto enter the station earlier or leave it later. If time savingsreach or exceed minimal time span when two trains passstraight one after another, regulated in the safety require-

ments and signaling systems, it becomes possible to insertadditional train rout of slower or faster train (see Fig 3).


3/7

1195

Fig 3. Influence of speed increment of the slower trains onthe capacity

In such case it is purposeful to evaluate the train ac-celeration in respect of saved (gained) minutes. Thus timesavings can be compared to a minimal interval betweentwo trains and sufficiency of the speed acceleration isestimated for insertion of additional train thus increment-ing the line capacity. This is not the only way to improvethe capacity however it is very important in order to op-timize the railway system in general.

Technical and control issues concerning the trainspeed are discussed in other chapters. Making properalterations capacity can be increased. Freight and passen-ger trains are analyzed separately because their workingprocesses are different.

3. Passenger trains

Local passenger trains are the slowest ones becausethey stop in every station. Speed limit in the lines anddistance between stoppages are not the only factors influ-encing common (working) speed. Three more factors can

be accentuated (Landex 2008; Abril et al. 2007):Traction and stopping characteristics;Speed limitations caused by technical reasons,

when trains enter or leave a station from the side-ways;

Stoppage duration.3.1. Traction characteristics

Assuming that the train can reach permissible dis-trict speed, additional time savings can be obtained ifacceleration and stopping (that does not have so much

influence) is increased. In figure 4 time savings are depic-ted (hatched area). They are obtained when the train trac-tion characteristics are improved. Savings of few secondsin a long district without intermediate stoppages do nothave influence on capacity. However total time savings oftrains that stop very often can markedly increase capacity.It is especially relevant in short districts where the trainswith better characteristics can reach and stand the maxi-mal line speed.

Calculation of train traction is needed for estimationof exact time savings. For this research a program Trac-tion has been used.

A passenger train can reflect main dependences. 16

trains with different parameters are chosen for the re-search. The trains are constructed using 4 different loco-

motives. Every of them are loaded with different loads:300 t (5 wagons); 600 t (10 wagons); 900 t (15 wagons);1200 t (20 wagons). Characteristics of the locomotivesare presented in table 1.

Fig 4. A diagram showing movement of trains with differ-

ent acceleration indicators in short and long districts

Table 1. Characteristics of locomotives

2TE10M TEP70 TEP60 M62

Length oflocomotive, m

34 22 19 18

Mass of lo-comotive, t

276 131 129 120

Weight oflocomotive, t

271 129 127 119

Constructio-nal speed,km/h

100 160 160 100

Calculatedspeed, km/h

23,4 48,3 47,0 20,0

Calculatedtraction force,kgj

50600 17000 12700 20000

Traction forcemaing a mo-ve, kgj

81300 29400 20500 35700

To determine more exact influence of the character-istics on travel time, traction calculations are done in thedistrict Gudagojis Vilnius kel.. It is assumed that thetrain will also stop in Kena, Kyviks and Naujoji Vilnia.After calculation of traction, travel time of every train ispresented in Table 2. These results are presented as a dia-gram (see Fig 5).

Table 2. Travel time of every train

Travel time, s

300 t 600 t 900 t 1200 t

2TE10M 36,2 38,2 40,3 42,5TEP70 35,6 39,6 43,5 47,1TEP60 37,3 42,6 47,2 51,3M62 40,1 45,6 50,5 55,0


4/7

1196

Fig 5. Dependence of travel time in the district Gudagojis Vilnius kel. on locomotives and loads

In this district of 45,288 km (lengths of the sidetracks: 16,184 km; 11,897 km; 8,03 km and 9,177 km)having 3 intermediate stoppages (average distance be-tween the intermediate stoppages is 11,322 km) traveltime of every train markedly differs. Figure 5 shows that

the travel time is highly dependent on loads and rollingstock traction characteristics. Thus importance of exactcalculation of passenger quantity and rational estimationof wagon and traction rolling stock amount is even moreemphasized.

The difference would be even larger if the distancebetween stoppages was less. However passenger traveltime savings are not as important as frequent stoppages(choosing locomotive with better characteristics) in popu-lous territories without disturbing high speed trains thatpass these districts.

3.2. Speed limitation at the approach to the station

To stop in a station it is ideal to start braking as lateras possible. When braking starts very early, time is lost.The longer the speed limitation zone the larger the timelosses. (Abril et al. 2007; Landex 2008). The speed limi-tation depends on: technical reasons switch type; safetyconditions in the dead-end stations or when slippagedistance is insufficient, speed limitations ensure trainstopping without negative results; regulations for e.g.speed limitations for a train intending to stop in a station.

In Figure 6 the hatched area depicts time losses orpossible time savings if limitations are eliminated. It isthe simplest example when movement of two trains is

calculated using different hypothesis. Possibilities to re-duce travel time are visible.

Fig 6. Influence of speed limitation at approaches to thestation on travel time losses

3.2.1. Limitations related to the switches

The largest stream of trains through Lithuania is bytransit. It means that the transit trains pass railway sta-tions nonstop and their speed decreases while passing

through the switches. Such situation results in decreasedtotal average speed. Consequently, having a purpose toincrease the train speed it is necessary to improve theswitch construction, technical conditions and mainte-nance (Gailienet al. 2008).

The speed limit entering the station is estimated re-ferring to the speed limitations that depend on the type ofswitch. Train speed is decreased when passing the switchthus making additional time losses.

The loss of time depends on the type of switch andon the distance between platform and switch point railend. Increment of the mentioned distance puts speed limi-tation forward. Therefore, when performing infrastructure

renovation, it is important to discuss possibilities to usethe switch of a proper type at the approaches to the sta-tions. Thus line and station capacity could be increased.

3.2.2. Speed limitation in the platform zone

Speed limitation is valid in the whole platformlength. Therefore time losses are highly dependent on theplatform length.

Figure 7 shows that the train stopping time losses aresmall when the platform is short however they increasewhen the platform length increases. Therefore they be-come very important, especially when difference of speedlimitation before the platform and speed limitation in the

platform is very big: ABCD < ABCD and ABEF

1193_1199_ramunas_gailiene_podagelis

Documents