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Leonid Engelson and Dirk van Amelsfort

The role of volume-delay functions in forecast and evaluation of congestion charging schemes Application to Stockholm. Leonid Engelson and Dirk van Amelsfort The Royal Institute of Technology and WSP Analysis and Strategy. Outline. Background of the project

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Leonid Engelson and Dirk van Amelsfort

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  1. The role of volume-delay functions in forecast and evaluation of congestion charging schemesApplication to Stockholm Leonid Engelson and Dirk van Amelsfort The Royal InstituteofTechnology and WSP Analysis and Strategy

  2. Outline • Background of the project • Model validation by effects of congestion charging • Adjustment of VDF • Results of the experiment • Conclusions and recommendations

  3. Background • Two research projects at CTS: • Improvement of CC system for Stockholm • Transferability of Stockholm experience to other cities • Need a model to calculate benefits of CC • Two state of the art regional models were used for forecasts • Destinationand mode choice • Static assignment • Comprehensive monitoring of CC effects • The observed effects differed from the model forecast • Is it possible to improve the model by small effort in order to be useful for CBA?

  4. The model • SAMPERS – a model for whole Sweden (5 regions, national, international), Stockholm + MD = oneof the regions • Nested logit demandmodel • 6 travel purposes • Frequency, destination, mode choice • Scalingdemandmatrices from daytoassignment period withfixedshares: AM peak, mid-day, PM peak • Scalingto 5 VoTclasseswithfixedshares • Transit and auto assignments in Emme • Auto assignmentwithgeneralizedcostwith 5 VoTclasses • Feedback traveltime and costto the demandmodel • VDF for Stockholm estimated 1979, adjustments in 80-s and 90-s • Travel survey 1990-1995

  5. The congestioncharging system

  6. Trafficflow over the cordon

  7. Comparison of modeled and observed effects, aggregate By Jonas Eliasson and Karin Brundell-Freij

  8. The cordon and the AVI links

  9. Comparison of modelled and observed effects, morning peak

  10. Demand model or supply model? • Flows change stronger than in reality. • Travel times change less than in reality • If flow changes are improved by better modelling the demand then the discrepancy in time changes will be even worse • The supply model needs improvement in the first hand

  11. To improve the static model • No interaction at intersections • No back propagation of queues • No queue building and dissipation (”average” conditions) • Still we can make VDF steeper in the static model (our VDF are from 1978) • Is it possible to calibrate a static model with a VDF slope parameter ? • Numericalexperiment

  12. Modificationof VDF time v0= flow in the base scenario guarantees that the assignment gives the same result in BA as with the original functions t0= time in the base scenario g f t0 v0 volume

  13. Effect of k on modelled traffic flow and average speed Still long to the observed ratio

  14. Effects of k on benefit of the CC (SEK per day) The benefit depends on k

  15. Comparison of charging systems with different k • The current system • The current system plus charge on Essinge bypass • The current system plus charge for crossing the strait • The current system plus charge for crossing the strait but not the Essinge bypass • The current system plus charge for crossing the strait plus charge on the Central bridge.

  16. Gate locations in the four alternative charging systems

  17. Ranking of different charging systems with k=1 and with k=10 (SEK per day) *1000 *1000 *1000 *1000

  18. Conclusions • Steeper VDF make the model better reproduce effects of CC • Even med much steeper VDF the model still underestimates the speed change to flow change ratio • With steeper VDF, the calculated benefit of CC is substantially higher than with the original VDF

  19. Recommendations • Static assignment models are not appropriate for CBA of CC in cities, more advanced tools are needed • When the benefit of CC is calculated with a static model the sensitivity analysis w r t slope of VDF is recommended (EMME macro is available)

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