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Carlos Espindola, Youssef Dehghani and Cathy Strombom Parsons Brinckerhoff, Inc.

Major Transportation Corridor Studies Using an EMME/2 Travel Demand Forecasting Model: The Trans-Lake Washington Study. Carlos Espindola, Youssef Dehghani and Cathy Strombom Parsons Brinckerhoff, Inc. October 18-20, 2000

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Carlos Espindola, Youssef Dehghani and Cathy Strombom Parsons Brinckerhoff, Inc.

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  1. Major Transportation Corridor Studies Using an EMME/2 Travel Demand Forecasting Model: The Trans-Lake Washington Study Carlos Espindola, Youssef Dehghani and Cathy Strombom Parsons Brinckerhoff, Inc. October 18-20, 2000 15th Annual International EMME/2 Users’ Group Conference, Vancouver, BC.

  2. Outline • The Project • The Alternatives • Mini Validation • Coding Challenges • Problems Encountered • Measures of Effectiveness • Looking Ahead • Acknowledgements

  3. The Project • Identify “reasonable and feasible solutions” to improve mobility across/or around Lake Washington • Three facilities were studied: SR-520, I-90 and SR-522 • Projected regional growth: 50% more person trips over the next 25 years • Using EMME/2 based four- step model (Puget Sound Regional Council)

  4. Study Area

  5. The Alternatives • 6 alternatives plus No-Build • No-Build • SR-522: 2 GP lanes in each direction • SR-520: 2 GP lanes in each direction • I-90: 3 GP lanes plus 2 reversible center lanes • Metropolitan Transportation Plan (MTP, 1998) • bus-only lanes on SR-522 • HOV lanes on SR-520 • LRT on I-90 center lanes • some TDM improvements

  6. The Alternatives (cont.) • MTP “Flipped” • new LRT bridge along SR-520 • continuous 2-way HOV lanes on I-90 center lanes • Roadway/Rail • new LRT bridge along SR-520 • LRT on I-90 center lanes

  7. The Alternatives (cont.) • New Crossings • a new four-lane arterial connection across the lake north of SR-520 and HOV lanes on SR-520 • LRT on new arterial bridge and on I-90 • Roadway/Bus • new four-lane freeway with HOV lanes • improved bus service & passenger only ferry • 2-way 24 hour HOV lanes on I-90 center lanes

  8. The Alternatives (cont.) • Maximize Alternatives • passenger-only ferry • conversion of one GP lane to HOV lane on SR-520 • LRT on I-90 center lanes • very aggressive TDM package including congestion-pricing measures

  9. Mini Validation • Screenline comparison of vehicle volumes: observed vs. modeled • Tolerance: + 10% • Highway Assignment • Data: AWDT • Daily variation of traffic volumes • Transit Assignment • Data: observed and Sound Transit (ST) model

  10. Coding Challenges • Transportation demand management • Equivalent parking cost • Congestion Pricing • Time equivalency of toll

  11. Problems Encountered • The “flip-flop” effect • What? Large variation in number of trips across the lake (validation) • Why? Caused by congestion (constrained capacity) in Trans-Lake facilities • How? Trip distribution (gravity model) reduces trips across the lake – search for equilibrium between supply and demand • Then? Consistency in application from one alternative to another

  12. Congestion Pricing • Feasibility of tolls on cross lake trips (demand management) • Cross lake demand got depressed (“lost” over 100,000 daily trips) • caused unrealistic demand estimates for transit and HOVs • What to do? • Introduce toll on assignment only • Or two step process

  13. Congestion Pricing (cont.) • Two step process • Suppressed demand for non-HOVs • Model run with toll, lane conversion and parking costs • Un-suppressed demand for HOVs and transit • Model run without toll, lane conversion or parking costs • Highway and transit assignments

  14. Measures of Effectiveness • To help evaluate and compare the performance of the alternatives • Vehicle trips by facility and mode (NCPL, HOV and Commercial vehicles) • Person trips by facility and mode (same as above plus Transit), screenline mode shares were produced • Weighted average PM peak period travel time in minutes between designated districts

  15. Measures of Effectiveness (cont.) • From select link analysis on each facility: • PM peak period vehicle miles of travel (VMT) • PM peak period vehicle hours of travel (VHT) • PM peak period speeds • weighted average trip lengths both in distance and time • Peak period and hourly vehicular traffic, capacity and v/c ratio by facility and direction • Peak period person through-put by facility, mode and direction

  16. Looking Ahead • Use of Composite Impedance in trip distribution to reflect both highway and transit improvements • Update base year (1998) • Define the use of “new” vs. current version of PSRC model • Look at better way to forecast 3+ HOVs

  17. Summary • A tool to identify “reasonable and feasible solutions” to improve mobility across/or around Lake Washington • Helps evaluate a wide variety of transportation improvements (focus on mode, location and amount of change)

  18. Acknowledgements • Washington State Department of Transportation – Office of Urban Mobility (WSDOT/OUM) • Puget Sound Regional Council (PSRC) • Trans-Lake Washington Consulting Team

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