UBC Theses and Dissertations
Evaluation of transit signal priority options for rapid transit and light rail transit in the city of Richmond Barton, Michael
Transit signal priority (TSP) involves modifications to traffic signal cycle plans in order to give preferential treatment to transit vehicles to reduce travel delay and, consequently, average travel times and variability in travel times. This can make transit a more attractive mode of transportation, which can result in travelers choosing public transit over low occupancy vehicles. One of the main goals of this thesis is to develop a strategy that maximizes the benefits of TSP by finding the best values for certain parameters, including TSP parameters such as length of the green extension provided to transit vehicles, implementation of phase skipping and unconditional versus conditional priority. There are also corridor properties, such as locations of transit stops, locations of check-in detectors and whether transit has a shared or exclusive travel corridor. The literature reviewed in this paper indicates that TSP can provide significant travel time improvements compared to a network of fixed or actuated traffic signals. However, there can be considerable impacts on cross street traffic operations since signal phases are disrupted with each action taken to provide TSP. The other main goal of this thesis is to compare the influence of TSP implementation on transit operations with an express bus system and a light rail transit system. In order to study the influence of different parameters TSP performance, a model has been developed to simulate traffic and transit operations in the No. 3 Road corridor in the City of Richmond. The results indicate that transit vehicle delay and travel time are inextricably linked, meaning that reductions in travel time are largely the result of reductions in delay. The results also indicate that use of phase skipping and the choice between conditional and unconditional TSP are among the most important considerations in TSP implementation. Phase skipping results in less transit delay and lower travel times than the same scenarios without skipping. However, phase skipping increases adverse impacts as more cross streets experience delay increases and the scale of the increases is greater than without skipping. Unconditional TSP provides lower transit travel times since every vehicle is given priority at every intersection regardless of the operational situation existing at the time. However, conditional TSP is more sensitive to cross street traffic operations and other operational parameters, such as signal coordination. The light rail transit system provides lower transit travel times than express bus since light rail vehicles (LRVs) experience less delay in traveling through the corridor than buses. This is mainly the result of shorter average dwell times for LRVs at transit stations and the fact that an LRT would operate in an exclusive right-of-way for the entire corridor, free of the influence of automobile traffic experienced by buses in shared travel segments of the corridor. Based on the study findings, the following recommendations are made. Far side transit stops should be used at all locations to limit transit delay and travel times and allow for efficient use of green extensions by transit vehicles. A green extension should be selected based on detector-to-intersection distance and travel speed of a transit vehicle. Phase skipping should be employed when the objective is to minimize delay experienced by transit vehicles. An LRT line will offer significant transit operational benefits if implemented. A cost-benefit analysis should be undertaken to determine if the considerable delay and travel time benefits of LRT relative to express bus justify the capital expenditures required for implementation.
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