MPC
Research Projects (2008-09)

Identifying Number

MPC-313

Project Title

Evaluation of LRT and BRT Impact on Traffic Operations in Salt Lake City Metropolitan Region, Year 1

University

University of Utah

Project Investigators

Aleksandar Stevanovic, Research Assistant Professor and Peter T. Martin, Professor

Description of Project Abstract

With ever-increasing traffic demand and price of fossil fuels public transit becomes more popular transportation mode than ever before, especially in the fast growing regions such as Salt Lake City Metropolitan Region. Wasatch Front Regional Council (WFRC) (a local Metropolitan Planning Organization) incorporated several LRT and BRT projects in its long-term regional transportation plans of 2015 and 2030. After initial success of Light Rail Transit (LRT) and Bus Rapid Transit (BRT) deployments to alleviate traffic congestion, the Utah Transit Authority (UTA) has planned to expand these services. New LRT and BRT services introduced by the UTA will both increase spatial coverage and frequency of overall transit services in the region. However, this increase in public transit coverage and frequency will come at the expense of conflict in priority with vehicular traffic. Goal of this project is to evaluate impact of extended public transit services on vehicular traffic in the region in future years.

Project Objective

The project objectives are (1) Define areas where potential conflict between public transit services and vehicular traffic will arise (potential areas are: 400 South LRT route, 5600 W & 3500 S, intersections of LRT and 2100 S and 1300 S). (2) Define criteria for assessing public transit impact on vehicular traffic. (3) Conduct a literature review of similar projects in the US. (4) Develop methodology to assess the public transit impact on vehicular traffic. (5) Design and conduct data collection. (6) Develop simulation models and scenarios for Transit Signal Priority (TSP) to support the evaluation. (7) Perform data reduction and analysis. (8) Recommend remedies for the operation at the conflict points (TSP, modified transit schedules, etc.).

Project Approach/Methods

VISSIM microsimulation software will be used to build high-integrity models of traffic and transit conditions for each scenario. The models will be based on the traffic and transit data collected in the field or from relevant government agencies (UTA and UDOT). There may be a need to use macroscopic transportation planning models to forecast future traffic flows and plan transit schedules. VISGAOST, new optimization software developed by Utah Traffic Lab, will be used to investigate various TSP strategies for the LRT and BRT lines. Existing TSP on some of the LRT routes will be modeled to establish base case scenarios. New TSP strategies will be modeled by using ASC/3 SILS and other methods (e.g. Vehicle Actuated Programming - VAP) to explore improvement for vehicular operations.

MPC Critical Issues Addressed by the Research

Focus Areas Addressed by Research:

FA 11 - Traffic Operations and Management; FA 14 - Multimodal Policy and Investment Assessment; FA 17 - Environmental Impacts of Infrastructure

FA 11 – Longer-term traffic strategies (introduction of BRT and 3-4 new LRT lines); innovative lane utilization (investigate justification for exclusive BRT lanes); traffic adaptive signal control systems (transit signal priority should be provided to almost all BRT and LRT services).

FA 14 – Benefit-costs analysis of transportation network investments (BRT on 3500 S spans over major NS highway and transit corridors, LRT on existing Sandy route spans over major EW corridors); multimodal interactions in capacity-constrained corridors (interaction between LRT and vehicular traffic may become a serious problem in a long-term in SLC downtown area).

FA 17 – Environmental impacts of alternative transportation modes for commuting.

Contributions/Potential Applications of Research

With an increase in spatial coverage and frequency, the transit services will significantly impact vehicular traffic. Expected number of trains at some intersections (e.g. 1300 S and 2100 S) will reach 24 trains per hour in both directions in the next years. Clearly, this number of trains (when compared with present 8 trains per hour) will significantly affect traffic operations at these intersections. Neither UDOT nor UTA know how to handle this situation. There may be a need for extensive TSP, adjustment of the train schedules, modifications of the signal timings, or even a need for infrastructure investments (two-grade separation) to provide smooth operations for both traffic and public transit. The evaluation project, supported by extensive modelling, will help UTA and UDOT to anticipate future operations and prepare viable ways of dealing with potential problems. Findings from the study will also help to plan future extensions of public transit operations in the areas near to Salt Lake City downtown.

Time Duration

July 1, 2008 – June 30, 2009

Total Project Cost

$140,763

MPC Funds Requested

$55,360