An Analytical Alternative to Transit Signal Priority Micro-simulation Modeling: Model and Application

The estimation of the expected performance of Transit Signal Priority (TSP) for a given intersection is not a trivial task given the large number of factors that influence the TSP operation. Previous studies have demonstrated that TSP is not always guaranteed to provide net benefits and the general traffic particularly on the non prioritized approach, is typically negatively impacted by the deployment of transit signal priority under all types of traffic signal control. In current practice, most traffic impact studies are conducted using microscopic traffic simulation models (such as VISSIM, PARAMICS, AIMSUN, etc.) that provide the ability to model in detail the roadway corridor, traffic signal operations, and vehicle movements (including transit vehicles). However, these simulation models require specialized expertise and significant effort to apply correctly – resources that are often not available in-house to transit agencies. This paper proposes an analytical model which can be used instead of of microscopic simulation models for estimating the impacts (delay, fuel consumption, and emissions) of implementing transit signal priority. The proposed model is suitable for implementation within a spreadsheet and requires considerably less effort, and less technical expertise, to apply than a typical micro-simulation model and yet provides estimates of performance impacts that are consistent with those obtained from simulation modeling. It is typical that the resources available for funding transit priority measures (including TSP) is much less than would be required to deploy TSP at all signalized intersection along even the major transit routes in a transit network. The usefulness of the model is demonstrated through the application of the proposed model to prioritize TSP deployment at sixteen signalized intersections in the Region of Waterloo, Canada. This paper is of particular interest to transit agencies or traffic engineering personnel who are responsible for identifying, evaluating and prioritizing locations for the deployment of transit signal priority.