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Capacity of Single-Track Railway Lines with Short Sidings to Support Operation of Long Freight Trains

Ivan Atanassov, C. Tyler Dick, Christopher P.L. Barkan

Rail Transportation and Engineering Center

University of Illinois at Urbana-Champaign

2014

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Research Problem The North American railroad network is projected to experience

increased demand for freight transportation in the coming decades

Use of distributed power locomotives in heavy-haul service has allowed for greater efficiencies through operation of longer freight trains

The majority of national mainline routes are single track; as a result, the potential economic and operational advantages offered by long trains are constrained by the inadequate length of many existing passing sidings

Characterize the interaction between lengths of passing sidings and trains, and the subsequent effect on track utilization and train delay

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Rail Traffic Controller Rail Traffic Controller (RTC) is the industry-leading rail traffic simulation software in

the United States, and is used by a wide range of public and private organizations, including most Class I railroads, Amtrak, and Bay Area Rapid Transit (BART).

Input

Track layoutSignalsSwitchesSpeed limitTrain consist

Output

Train delayDwellSiding usage countsTrain performance calculatorTime-space diagram

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Simulated Route and Freight Train Characteristics

Route Characteristics Values

Length 240mi.

Siding Spacing 10mi.

Total No. of Sidings 23

Siding Lengths 1.25mi. (short), 2mi. (long)

Traffic Composition 100% Freight

Locomotives SD70 (x2 or x3) 

No. of Cars 100 (short train), 150 (long train)

Total Length of Cars 5,500ft. (short train), 8,250ft. (long train)

Max. Freight Speed 50mph (45mph through siding)

Traffic Control System 2-block, 3-aspect CTC

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Experiment Design Factors and Levels

Experiment Design Factors No. of Levels Level Specification

Percent Long Sidings 140, 4, 9, 13, 22, 30, 48, 52,

70, 78, 87, 91, 96, 100

Percent Long Trains 4 0, 25, 50, 75

Directional Distribution 250-50 (bi-directional),100-0 (uni-directional)

Freight Throughput 2 3,600 cars & 2,400 cars

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Examples of Balanced Long Siding Distributions

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Delay as a Function of Percent Long Sidings

To operate with a high percentage of long trains, only half of the sidings on a route need to be extended in order to maintain the baseline level of service

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Delay Variance as a Function of Percent Long Sidings

Simulated delay values become relatively consistent when the route has at least 20 percent long sidings

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Uni-Directional Long Trains

Long train operations that are fully uni-directional have no significant delay impact; an uneven directional distribution of long trains, however, produces a familiar delay trend

3,600-Car Throughput

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Influence of Long-Train Directional Preference

The case with long train directional preference follows the same delay patterns as those for the even, bi-directional cases, converging again to a point at roughly 50 percent long sidings

3,600-Car Throughput

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Future Directions Investigate a broader range of freight throughput values to

determine the consistency of the free-flow point of 50 percent long sidings

Investigate train and siding length relationships on routes with uneven siding spacing

Introduce heterogeneity in the form of passenger trains to the simulations

Extend the issue of long trains to yard & terminal requirements, and the subsequent interaction with mainlines

Train length extension of analytical Optimal Siding Location Model

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AcknowledgmentsTechnical collaboration and assistance from:

Mei-Cheng Shih, Taşkın Şehitoğlu, Samuel Sogin, Xiazhi Zhang

This research supported by:

National University Rail Center (NURail) a USDOT-OST Tier 1 University Transportation Center

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Thank YouIvan Atanassov

Graduate Research AssistantRail Transportation and Engineering Center (RailTEC)

University of Illinois at Urbana-ChampaignE-mail: atanass1@illinois.edu