Benefit

Schedule adherence and speed-based transit signal priority system in Minneapolis reduced travel times by 3 to 6 percent more than a traditional transit signal priority system on the same route.

Results of a Transit Signal Priority field test in Minneapolis, MN.


October 2011
Minneapolis,Minnesota,United States


Summary Information

Many transit priority systems (TSP) are based on the systems that give emergency vehicles signal preemption based on sensor detection or crossing a threshold near a signal to allow the vehicle to experience an extended green or shorter red cycle to move the emergency vehicle through the intersection. Because transit buses do not always need to go immediately through a traffic signal, because it is making a near-side stop, this system is suboptimal for giving transit vehicles the appropriate type of signal priority.

A two week field test of a new TSP system along a 5.5 mile corridor was done in Minneapolis, Minnesota in 2011 by the University of Minnesota (UMN) as part of the Urban Partnership Agreement. The test evaluated the travel times of buses equipped with a new algorithm that factors in schedule adherence, location, and speed (UMN TSP) against the travel times of the buses on the same route that are equipped with the existing TSP system (EMTRAC), which does not account for bus readiness or schedule adherence.

Methodology
Based on stop location (nearside vs. farside), schedule adherence, predicted dwell time, and headway spacing, the UMN developed an algorithm that uses the in-vehicle computer to determine whether to send a wireless message to the traffic signal to request priority.

Bus route 10, which runs along Central Avenue where TSP was already implemented, was selected for the field test. The 5.5 mile stretch has 27 signals and 39 bus stops between 2nd Street SE and 53rd Avenue NE and all signals have TSP capabilities. The TSP systems will only respond to requests when it has been more than 8 minutes since the last request (headway limitation) or a bus is more than 3 minutes late (lateness threshold) in order to reduce the impact on side street traffic (limitations as of Nov. 2010). Performance of four buses running the UMN TSP algorithm were compared to the other Route 10 buses operating during the two week test period (3/28/2011 - 4/8/2011).

Findings
  • For northbound trips, the UMN TSP equipped buses had a mean trip travel time of 22.12 minutes, compared to 23.63 minutes for the existing TSP system, a 6.4 percent reduction.
  • For southbound trips the UMN buses had a mean travel trip time of 22.79 minutes, 0.61 minutes faster than the existing system, a 2.6 percent reduction.

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Source

Field Testing and Evaluation of a Wireless-Based Transit Signal Priority System

Author: Chen-Fu Liao and Gary A. Davis

Published By: Intelligent Transportation Systems Institute Center for Transportation Studies University of Minnesota

Source Date: October 2011

URL: http://conservancy.umn.edu/bitstream/117369/1/CTS%2011-25.pdf

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Goal Areas

Mobility

Typical Deployment Locations

Metropolitan Areas

Keywords

bus priority, traffic signals, TSP

Benefit ID: 2012-00814