BUS TRANSIT PRIORITY: MODELING AND EVALUATING PERFORMANCE

Open Access
- Author:
- Wu, Kan
- Graduate Program:
- Civil Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 22, 2019
- Committee Members:
- S. Ilgin Guler, Dissertation Advisor/Co-Advisor
Vikash V. Gayah, Committee Chair/Co-Chair
Martin T. Pietrucha, Committee Member
Terry L. Friesz, Committee Member
Terry L. Friesz, Outside Member - Keywords:
- bus transit priority
transit signal priority
traffic flow theory
kinematic wave theory
queuing theory - Abstract:
- Urban congestion is a problem that plagues many different cities. One solution is to improve bus operations by prioritizing them to make this mode more attractive. Since buses can carry more people than private vehicles in the same amount of space, more users of the bus mode can help mitigate urban traffic congestion. Hence, bus priority strategies have been deployed in many cities. Two commonly used bus priority strategies are transit signal priority (TSP) and dedicated bus lanes (DBL). This thesis focuses TSP strategies with or without dedicated bus lanes. Dedicated bus lanes alone are not studied since this priority method can significantly reduce car capacities if a lane is taken away from general traffic. In general, the impacts of TSP strategies are two-fold: 1) benefits to bus transit service, including reduced delays, increase in reliability and decrease passenger waiting time, and 2) impacts to car traffic, including both the detriment to cross street cars and benefits to arterial street cars. These impacts are not independent since buses and cars use the same space on the roadway and interact with each other. This thesis uses theoretical approaches, such as the kinematic wave theory (KWT) and its variational forms (variational theory (VT) and Lax-Hopf numerical scheme), to analytically model TSP impacts. These models are then used to evaluate the applicability of TSP in different scenarios. Two levels of analysis are considered in this thesis: 1) an isolated intersection, and 2) an arterial consisting of multiple intersections in a series. At an isolated intersection, a numerical analysis utilizing variational theory unveils the trade-off between delays to cars and buses while implementing TSP, for both oversaturated and under saturated traffic conditions when buses and cars travel at the same speed. These models are also used to understand how bus stop locations and bus dwell durations can change the impacts of TSP. Next, the assumption that buses and cars travel at the same speed is relaxed and a KWT-based numerical scheme that solves the Lax-Hopf model is used to evaluate TSP impacts. This model is used to evaluate the sensitivity of TSP to bus stop location, bus dwell duration, and bus detection technology. At the arterial-level, the Macroscopic Fundamental Diagram is first used to quantify the change in car throughput and change in bus travel time for a combined TSP and DBL strategy. Next, the KWT-based numerical scheme to model the changes in car delays and bus travel times is used to understand the impacts of TSP in the absence of dedicated bus lanes. These analytical models are used to optimize locations of TSP implementations to maximize bus benefits and minimize increase in car delays.