Major Transportation Corridor Studies Major Transportation Corridor Studies Using an EMME/2 Travel Demand Using an EMME/2 Travel Demand Forecasting Model: The Trans-Lake Forecasting Model: The Trans-Lake Washington StudyWashington Study

Carlos Espindola, Youssef Dehghani

and Cathy StrombomParsons Brinckerhoff, Inc.

October 18-20, 2000

15th Annual International EMME/2 Users’ Group Conference, Vancouver, BC.

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OutlineOutline

The Project The Alternatives Mini Validation Coding Challenges Problems Encountered Measures of Effectiveness Looking Ahead Acknowledgements

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The ProjectThe 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)

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Study Study AreaArea

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The AlternativesThe 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

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The Alternatives (cont.)The Alternatives (cont.)

MTP “Flipped”– new LRT bridge along SR-520– continuous 2-way HOV lanes on I-90

center lanesRoadway/Rail– new LRT bridge along SR-520– LRT on I-90 center lanes

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The Alternatives (cont.)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

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The Alternatives (cont.)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

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Mini ValidationMini 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

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Coding ChallengesCoding Challenges

Transportation demand management– Equivalent parking cost

Congestion Pricing– Time equivalency of toll

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Problems EncounteredProblems 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

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Congestion PricingCongestion 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 HOVsWhat to do?– Introduce toll on assignment only– Or two step process

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Congestion Pricing (cont.)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

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Measures of EffectivenessMeasures 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

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Measures of Effectiveness (cont.)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

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Looking AheadLooking 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 modelLook at better way to forecast 3+

HOVs

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SummarySummary

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)

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AcknowledgementsAcknowledgements

Washington State Department of Transportation – Office of Urban Mobility (WSDOT/OUM)

Puget Sound Regional Council (PSRC)

Trans-Lake Washington Consulting Team