A minimum delay approach to maximum bandwidth optimization on arterial traffic signal timing

Abstract

This dissertation was to develop and evaluate the effectiveness of modifications to the PASSER II signal timing plan for an arterial street system using both a MAXIMUM BANDWIDTH procedure and a MINIMUM DELAY signal timing optimization algorithm. It was to find an efficient and usable delay-based search algorithm for selecting a minimum-delay arterial street signal timing plan that optimizes the phasing sequence, cycle length, and offsets based on maximum-bandwidth calculations. The research effort was directed toward several major topics included: (1) development of a practical procedure which could be used to fine-tune the offsets of traffic signals to minimize total delay and maximize progression of traffic in a progressive system; (2) development of methods that can better estimate vehicular delay in a nearly saturated traffic system in an urban network. An enhanced version of the popularly used PASSER II-80 program, PASSER II-84, was programmed and documented. This study found: (1) PASSER II-84 consistently outperformed PASSER II-80 based on PASSER II and NETSIM evaluations. (2) Consistent and satisfactory trend in predictions of delay were found between PASSER II-84 and NETSIM. (3) PASSER II-84 reduced total system delay from 0 to 4 percent for the thirteen (13) test scenarios. Arterial movement delays were reduced from 0 to 23 percent according to NETSIM than the PASSER II-80. (4) No apparent correlation was found between average arterial system delay reduction and progression efficiency. (5) Rather than using the total directional traffic volume ratio and minimum green time constraint alone to provide the best directional bandwidth weighting, an optimization search outside the existing slack time allowance ranges can further reduce the total arterial system delay by slightly varying the optimal progression solution. Overall, the results of fine-tuning offsets confirmed the feasibility and benefits of minimizing delay by adjusting offsets based on the optimal setting calculations from the maximum bandwidth algorithm. When minimum delay and maximum progression are used, as calculated by the enhanced PASSER II-84, an improved level of service results. This study indicated the advantages and drawbacks of combining the two major state-of-the-art traffic signal control strategies; i.e., the bandwidth maximization procedure and the delay minimization technique.