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Karen Tsang Bureau of Transport Statistics Department of Transport May 2011

Comparison of EMME Transit Assignment Methods Optimal Strategies vs Strategies with Variants (path assignment). Karen Tsang Bureau of Transport Statistics Department of Transport May 2011. Overview. A series of transit assignment experiments ◦ Compare standard and new methods

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Karen Tsang Bureau of Transport Statistics Department of Transport May 2011

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  1. Comparison of EMME Transit Assignment MethodsOptimal Strategies vs Strategies with Variants (path assignment) Karen TsangBureau of Transport Statistics Department of Transport May 2011

  2. Overview A series of transit assignment experiments ◦ Compare standard and new methods ◦ To understand how flows are distributed ◦ Using simplified network (2 transit services) ◦ Variables : in-veh time, wait time, headway choice between centroid connectors Sydney Strategic Travel Model (STM) Network ◦ Rail Assignment Example

  3. Standard vs New

  4. Standard vs New STANDARD NEW

  5. Experiment 1: • Demand from origin to destination = 100 passengers • No auxiliary (walk) link choice • New service variables • Headway: 5, 10, 15 and 20 minutes • Travel time: 1 to 40 minutes in 1 min interval • Percentage of passengers using New service?

  6. Experiment 1: • Assignment attributes and weighting factors: • In-vehicle time factor = 1.0 • Auxiliary (walk) travel time factor = 2.0 • Wait time factor = 2.0 • Wait time = Headway/ 2 • Boarding time = 5 min • Boarding time factor =1.0

  7. Experiment 1: STANDARD Distribution of flows based on frequency NEW Distribution of flows based on frequency and transit time

  8. Experiment 2: Reduced wait time weight Wait time weight = 2.0 (Experiment 1) Wait time weight = 1.0 (Experiment 2)

  9. Experiment 2: Reduced wait time weight STANDARD Wait time weight = 1.0 STANDARD Wait time weight = 2.0 Results from Experiment 1

  10. Experiment 2: Reduced wait time weight STANDARD Wait time weight = 1.0 Flow distribution based on frequency NEW Wait time weight = 1.0 Flow distribution based on frequency and transit time

  11. Experiment 3: Choice between connectors • Demand from origin to destination = 100 passengers • Choice between 2 centroid connectors • New service variables • Headway: 5, 10, 15 and 20 minutes • Travel time: 1 to 40 minutes in 1 min interval • Percentage of passengers using New service?

  12. Experiment 3: Choice between connectors STANDARD One service route is chosen All or nothing NEW Two centroid connector choices Option 2 (logit) Scale parameter = 0.2 (default) where exp(-scale * transit time to destination)

  13. Experiment 3: Choice between connectors STANDARD One service route is chosen All or nothing NEW Two centroid connector choices Option 2 (logit) Scale parameter = 0.5 where exp(-scale * transit time to destination)

  14. Experiment 3: Choice between connectors STANDARD One service route is chosen All or nothing NEW Two centroid connector choices Option 2 (logit) Scale parameter = 0.8 where exp(-scale * transit time to destination)

  15. Experiment 3: Choice between connectors STANDARD One service route is chosen All or nothing NEW Two centroid connector choices Option 2 (logit) Scale parameter = 1.0 where exp(-scale * transit time to destination)

  16. Distribution of flows to attractive lines Standard: based on frequency New: based on frequency and transit time (optional) Distribution of flows between connectors at centroids Standard: one path with best generalised time (AON) New: multiple paths at centroid connectors (optional) Key Differences

  17. Experiment Results • Flow Distribution on attractive lines • Standard = Step function • New = Step with transition logit curve • Flow Distribution between multiple centroid connectors • Standard = AON • New = AON or multiple preferred paths

  18. Sydney Strategic Travel Model (STM) • Rail Network • Rail Stations: • Over 340 • Rail Transit Lines: • 80 (approx) • Rail Link Length: • Approx 2400 km

  19. Sydney Strategic Travel Model (STM) • Rail Line Example

  20. Sydney Strategic Travel Model (STM) Rail Lines (Entire Network)

  21. STM Network - Rail Assignments • Fixed Demand: 3.5-hr rail AM demand • Network: Rail Network with walk and bus access/egress • Assignment Methods: • Travel zone to Travel zone assignments • Standard Assignment – Optimal Strategies • Strategies with Variants • – Path Saved • – Distribution of flows based on frequency and transit time • – Scale Parameter = 0.5

  22. Rail Assigned Volumes Method 1: Optimal strategies (standard)

  23. Rail Assigned Volumes Method 2: Strategies with variants (new)

  24. Rail Assigned Volume Differences • Green = • Less volumes in new method • Red = • More volumes in new method -6 % +4 % +1 % +4 %

  25. Conclusions: Rail Assignment • Rail assignment differences up to +/– 6% • Minimise back-tracking • Retain fast assignment run time • Standard = 1 minute, New = 2 minutes • Increase attractiveness of express services

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