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, th 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