Major Transportation Corridor Studies Using an EMME2 Travel Demand Forecasting Model: The TransLake

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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.
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Outline

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

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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)

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Study Area
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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

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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

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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.)

• 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 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 Challenges

• Transportation demand management
• Equivalent parking cost
• Congestion Pricing
• Time equivalency of toll

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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

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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

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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 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.)

• 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 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

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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)

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Acknowledgements

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