1. © APTA and AREMA - 2015 2-D Introduction to Railway Capacity C. Tyler Dick, P.E. University of Illinois at Urbana-Champaign

2. © APTA and AREMA - 2015 Outline Introduction Basic Rail Capacity Concepts Analytical Models of Railway Capacity Parametric Models Simulation Models Optimization Models Other Considerations and Expansion Strategies 2

3. © APTA and AREMA - 2015 Fields Related to Capacity Analytics Data mining Network optimization Queuing theory Regression modeling Risk modeling Simulation Utility models 3

4. © APTA and AREMA - 2015 Railroad Capacity Over Time 19 th and early 20 th century: Great expansion of railroads World War I: War traffic brought network to standstill due to insufficient capacity due to inefficient operations 1920s: Relative balance between capacity and traffic levels Great Depression: Loss of traffic led to excess capacity World War II: Congestion from war traffic After WWII: Overcapacity as passenger and freight traffic declined 1990 - Current: Growth in traffic and market power has permitted railroads to spend substantial amounts to remove choke points 4

5. © APTA and AREMA - 2015 Increasing Demands on Rail Network 5 Reliability Intercity Passenger Trains Commuter Service Low Cost Transportation Freight Growth Environment Cambridge Systematics. (2007). National Rail Freight Infrastructure Capacity and Investment Study.

6. © APTA and AREMA - 2015 Problems of Capacity Shortages Inability to handle more traffic Decreasing level of service Diminished ability to recover from a disruption Limited windows for track maintenance Increase time in yards, terminals and stations Increase cycle times Increase number of trainsets, rolling stock Increase number of crews (hours of service limitations) All of the above increase costs 6

7. © APTA and AREMA - 2015 Capacity is an Expensive Resource Railway infrastructure is capital intensive and a long-term investment Capacity lags behind changing demands 7 Capital Investment as a % of Revenue

8. © APTA and AREMA - 2015 Levels of Capacity Analysis Transportation Network Railroad Network Subdivision or Line Yards & Terminals Stations & Platforms Interlockings & Junctions 8

9. © APTA and AREMA - 2015 Types of Capacity Practical Capacity: Ability to move traffic at an “acceptable” level of service Economic Capacity: The level of traffic at which the costs of additional traffic outweighs the benefits Engineering Capacity: The maximum amount moved before the system ceases to function Ultimate Capacity: Breakdown conditions at maximum train density. The system has ceased to function and all signals are red 9

10. © APTA and AREMA - 2015 What Should Capacity Measure? 10

11. © APTA and AREMA - 2015 Railway Capacity Metrics 11 Amount MovedReliabilityUtilization Trains Railcars Gross Tons Revenue Tons Passengers TEUs (Per Year) (Per Day) (Per Hour) (Per Peak Hour) Distribution of Arrival Times Average Delay Standard Deviation of Delay On Time Performance Right Car Right Train Crew Expirations Velocity Terminal Dwell Blocking Time Signal Wake Train Miles/Track Mile Cycle Time Trainsets or Railcars On-Line Track Occupation Train Density

12. © APTA and AREMA - 2015 Unlike highways, there is no standard railroad capacity model The complex nature of railroad operations and limited research funding has prevented a universal capacity model from being developed Currently several different models are in use 12

13. © APTA and AREMA - 2015 Level of Service to Measure Capacity Higher delays correspond to a lower level of service (LOS) Maximum theoretical train volumes are never reached due to deteriorated level of service Acceptable level of service establishes maximum train volume 13 Abril, M., Barber, F., Ingolotti, L., & Salido, M. (2008). An assessment of railway capacity. Transportation Research Part E: Logistics and Transportation Review, 44(5), 774-806.

14. © APTA and AREMA - 2015 Different Traffic and Track Configurations will Change Delay- Volume Relationship 14 Acceptable Delay Volume (Trains/Day) Delay (mins)

15. © APTA and AREMA - 2015 Track Configuration Number of tracks Siding length Siding spacing (distance & time) Crossover spacing Single crossovers Universal crossovers Parallel crossovers Geometry Grade Curvature 15

16. © APTA and AREMA - 2015 Double-Track Operations: Headway Common on most transit and some commuter rail operations Each track has a dedicated “current of traffic” with trains separated by a minimum headway Headway is a function of safe braking distance and signal spacing or control block length Very high capacity if all trains in one direction travel at the same speed (i.e. no passing) 16

17. © APTA and AREMA - 2015 Blocking Time Model Single direction on double track 17

18. © APTA and AREMA - 2015 Double-Track Analytical Model: Maximum Throughput Calculation The maximum traffic flow that a rail line can accommodate under ideal condition Where: N = Number of trains per day 1440 = Number of minutes in a day H min = Minimum headway (minutes) 18

19. © APTA and AREMA - 2015 Heterogeneous Train Speeds Passenger trains travel at higher speeds than freight trains Speed differential leads to decreased capacity Passenger train on freight corridor Freight train on passenger/commuter corridor 1 minority train consumes 3 majority train slots 19 Time Distance Time Distance

20. © APTA and AREMA - 2015 Overtakes on Double Track Passenger or commuter trains may experience additional delay while trailing behind slower trains If control system allows, faster trains can use opposite track to overtake slower trains Interrupts flow of traffic in opposite direction, decreasing overall capacity A passenger train requires over 40 miles to pass a freight at track speed without delay to either train 20

21. © APTA and AREMA - 2015 Single-Track Operation: Meet and Pass Single track poses significantly more challenges for practical railway capacity No longer simply limited by train spacing Must consider “meets” of trains traveling in opposite direction These impose constraints on schedule 21

22. © APTA and AREMA - 2015 Meets on Single Track 22

23. © APTA and AREMA - 2015 Meets on Single Track 23

24. © APTA and AREMA - 2015 Meets on Single Track 24

25. © APTA and AREMA - 2015 Single-Track Analytical Model: Return Grid Calculation for Meets Capacity of single track with meets C = Capacity in trains per day 1440 = Number of minutes per 24 hours t = Minutes to travel between sidings t/2 =Average dwell time waiting for opposing train to arrive m = Delay for each meet due to braking, entering the siding, running the length of the siding, leaving the siding and accelerating to speed 2 = number of trains per pair 25

26. © APTA and AREMA - 2015 Calculation Methodology 26 Siding A Siding B Time t Time 0 Time t+m Time 2t+m+t/2 Time t+m+t/2

27. © APTA and AREMA - 2015 Impact of Different Types of Trains Differing train operating speeds causes deviations from regular return-grid model, decreasing capacity 27 Time Distance Intermodal Amtrak Manifest Unit Time

28. © APTA and AREMA - 2015 Overtakes on Single Track 28 Time T2T2 Pass Delay

29. © APTA and AREMA - 2015 Heterogeneous Operations and Capacity Simple headway and grid models only work when all trains operate at the same speed Actual trains have different Operating speed Acceleration and braking characteristics Priority Station stopping patterns Particularly apparent where passenger and freight operations share track infrastructure From a capacity perspective: 1 freight train ≠ 1 passenger train These differences decrease capacity and require more complicated capacity analysis tools 29

30. © APTA and AREMA - 2015 Parametric Models Parametric Models are developed from statistical analysis of collected operating or simulation data Key infrastructure and operating parameters are identified to predict a delay-volume curve Attributes include Average speed Speed ratio Priority Peaking Siding spacing and uniformity Percent double track Signal spacing FRA and CN have well-known parametric models 30

31. © APTA and AREMA - 2015 CN Parametric Model Example 31 Average Speed44.4 mphSpeed Ratio1.113 Priority0.342Peaking1.727 Siding Spacing7.77 milesUniformity0.49 Signal Spacing0.93% Double Track50 Krueger, H. “Parametric Modeling in Rail Capacity Planning.” Proceedings of the 1999 Winter Simulation Conference. Phoenix, 1999. 1194-1200. Web. 21 May 2012.

32. © APTA and AREMA - 2015 Railway Simulation Tools Calculate train movements and make decisions under the same rules as railroad dispatchers Account for different equipment types, train consists, train handling characteristics, terrain and track conditions Common uses of Simulation Tools: Develop operating plans Diagnose bottlenecks and recommend schedule changes Evaluate various capital improvement scenarios Assess the impact of adding new trains to a network Many simulation models are available depending on the purpose and task of the study 32

33. © APTA and AREMA - 2015 Types of Simulation Tools Passenger timetable development (passenger) OpenTrack Viriato Specify timetable and identify conflicts RailSYS RailEval Non-timetable (freight) and resolve conflicts with dispatching logic Rail Traffic Controller 33

34. © APTA and AREMA - 2015 Optimization Models Identify required system settings to achieve an optimal level of performance Can become computationally complex for large railway networks with multiple train types Example applications Passenger timetable development Station platform and track assignment Rolling stock and crew cycles Infrastructure investments for running time improvement on shared corridors 34

35. © APTA and AREMA - 2015 Strategies to Increase Capacity Operations options: Increase average speed Reduce traffic peaking Reduce the variability in speed Reduce number of meets & passes Increase length & weight of trains Improved acceleration and braking Scheduling Infrastructure options: Add or lengthen passing sidings Additional tracks Add staging and terminal tracks Add station platforms Improve junction design Grade separations 35

36. © APTA and AREMA - 2015 Passenger Scheduling Strategies Fleeting Train Type: Reduce delays due to different train types operating on the same line Train Direction: Reduce delays on single tracks lines by reducing the meet delay Express and Skip-Stop scheduling Decrease travel time by bypassing intermediate station and terminals Minimize conflicts with trains in the same direction 36

37. © APTA and AREMA - 2015 Incremental Capacity of Infrastructure Expansion 37 Volume (trains/day) Delay (hours) directional running, DT bidirectional running, DT ST, siding every 21.4 miles Kahn, Ata M. Railway Capacity Analysis and Related Methodology. Ottawa, 1979. Print.

38. © APTA and AREMA - 2015 But at what cost? New passing siding $8 million and up Second main track $1 million per mile for rail, ties and ballast $4-6 million per mile depending on embankment, drainage and signals Bridges, grade separations and tunnels can quickly increase costs 38

39. © APTA and AREMA - 2015 Other Capacity Factors Mainline capacity consumed by Local service to freight rail customers Deadhead and repositioning moves Passenger boarding delays Locomotive and rolling stock failures Track inspection Track maintenance Difference between practical and engineering capacity 39

40. © APTA and AREMA - 2015 Rail Capacity Research Needs Models that capture yard-mainline interaction Predicting the impact of higher speed passenger and freight trains on the same corridor Creating new theoretical & parametric models 40

41. © APTA and AREMA - 2015 It is the author’s intention that the information contained in this file be used for non-commercial, educational purposes with as few restrictions as possible. However, there are some necessary constraints on its use as described below. The materials used in this file have come from a variety of sources and have been assembled here for personal use by the author for educational purposes. The copyright for some of the images and graphics used in this presentation may be held by others. Users may not change or delete any author attribution, copyright notice, trademark or other legend. Users of this material may not further reproduce this material without permission from the copyright owner. It is the responsibility of the user to obtain such permissions as necessary. You may not, without prior consent from the copyright owner, modify, copy, publish, display, transmit, adapt or in any way exploit the content of this file. Additional restrictions may apply to specific images or graphics as indicated herein. The contents of this file are provided on an "as is" basis and without warranties of any kind, either express or implied. The author makes no warranties or representations, including any warranties of title, noninfringement of copyright or other rights, nor does the author make any warranties or representation regarding the correctness, accuracy or reliability of the content or other material in the file. Copyright Restrictions and Disclaimer Presentation Author 41 C. Tyler Dick, P.E. Senior Railway research Engineer University of Illinois at Urbana-Champaign 205 North Mathews Ave Urbana IL 61801 217-300-2166 ctdick@illinois.edu Department of Civil and Environmental Engineering