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Transit Signal Priority (TSP) Research Project

Principal Investigator: Gary Davis, Dept. of Civil Engineering, drtrips@umn.edu
Co-Investigator: Chen-Fu Liao, Minnesota Traffic Observatory, cliao@umn.edu

Research Objectives:

  • Conduct traffic modeling and simulation to analyze and evaluate the impact of an adaptive TSP strategy
  • Bus transmits signal priority request to traffic controller based on its readiness not presence.
  • Use GPS/AVL system and wireless communication based adaptive signal priority system.
  • Develop a wireless TSP prototype system and validate the TSP algorithm developed from simulation study
  • Evaluate the performance of the deployed system as compared to other TSP deployments in the United States.
  • Evaluate the reliability and limitation of our system and identify the influencing factors, such as bus stop location, traffic conditions, and actuated or fixed-time signal control that will affect the TSP performance.
 Figure of UMN TSP system using AVL/GPS and wireless communications

UMN TSP system using AVL/GPS and wireless communications

Phase 1 (2005- 2006): Bus Signal Priority Based on GPS and Wireless Communications

The phase one study primarily focused on efforts to develop a simulation model in order to investigate the benefit and impact. A microscopic traffic simulation package, AIMSUN (Advanced Interactive Microscopic Simulator for Urban and Non-urban Networks) was selected for this study. A C++ program was developed to interface with the microsimulator through the Application Programming Interface (API). Bus location, speed, and bus stop information can be sent to the external bus signal priority application, and a priority request can be sent back to the simulator, in real-time. Metro Transit bus route #2, operating on Franklin Ave from S Dupont Ave to S 27th Ave in City of Minneapolis, was selected for the bus signal priority study. This study site consists of 42 intersections (22 signalized intersections) with total travel distance of about 3 miles each direction.

Simulation results indicate a 12-15% reduction in bus travel time during AM peak hours (7AM-9AM) and 4-11% reduction in PM peak hours (4PM-6PM) could be achieved by providing signal priority for buses. Average bus delay time was reduced in the range of 16-20% and 5-14% during AM and PM peak periods, respectively. The signal priority strategy caused increases of travel time for non-transit vehicles of about 6 seconds per vehicle during AM peak and 22 seconds in PM peak periods in average. The average number of non-transit vehicle stops increased from 1.6 stops per vehicle to 1.7 stops per vehicle during AM peak hours and from 2.0 stops per vehicle to 2.4 stops per vehicle during PM peak period.

Franklin_2 zoomed out
closer view of map

Phase 1 simulation study

Phase 2 (2006-2008): Bus Signal Priority on GPS and Wireless Communications - Phase II

The goals of the phase 2 study are to evaluate the performance of DSRC (Dedicated Short Range Communication) and Wi-Fi network, develop wireless communication prototype using commercial off-the-shelf (COTS) products, implement adaptive TSP algorithm and validate the signal priority strategy based on the AVL/GPS and wireless technology. City of Minneapolis recently deployed wireless technology to provide residents, businesses and visitors with wireless broadband access anywhere in the city. Communication with the roadside equipment (e.g., traffic controller) for signal priority was tested using the available 802.11x Wireless Local Area Network (WLAN) or the DSRC modems in vehicular environment. A set of PC/104 stand-alone Single Board Computer (SBC) was selected for the embedded system development. Additional I/O modules were integrated to the embedded system to perform data communication between traffic signal controller and roadside computer, and a transit vehicle and onboard computer. Field testing results show that the test vehicle successfully submitted signal priority request through the wireless communication as it is traveling toward the intersection instrumented with roadside equipment.

Field testing at SE Como and 29th Avenue

Field testing at SE Como and 29th Avenue

Phase 2 field testing results

Phase 2 field testing results

Phase 3 (2008-2009): Bus Signal Priority Based on GPS and Wireless Communications – Bus to Roadside Infrastructure Communication Framework for Intelligent Transit Applications.

We aim to develop and deploy the UMN TSP systems to at least four intersections along an arterial to evaluate the impact and benefit of the wireless-based signal priority algorithm and validate the capacity of wireless communication network. Transit delay at intersections will be measured and compared with the delay without priority. The delay reduction will also be compared to the TSP deployment in other cities as published in the literature. TSP system performance influenced by the traffic condition and near or far side bus stop will be investigated. We will also evaluate the reliability and limitation of our system and its influencing factors on overall TSP performance.

Contact: Chen-Fu Liao.