| The problem of controlling traffic signals---deciding when to allow vehicles to cross an intersection---dates back to the origin of vehicular transportation. The availability of detectors that transmit information on the real-time traffic status, and microprocessors that process this data, led to the development of adaptive, real-time traffic control systems. The superiority of adaptive traffic signal control over the traditional approaches is now widely recognized. The literature suggests that on average a 15--20% improvement in operation can be expected when adaptive control systems replace older systems.; The City of Vancouver, Washington implemented an adaptive control system for traffic signal operations at 12 intersections along Mill Plain Blvd. Performance measurement of this system was the main objective of this research. Link, intersection, and travel-time data were compiled and statistically analyzed. Multivariate regression modeling, analysis of variance and other tests were used to compare performance of the system in the control case (time of day signal control) and the treatment case (adaptive signal control). In addition, data observed from travel-time runs (collected via a "floating car") and data collected from system detectors were used to develop several regression models to further examine the correlation between various measures of effectiveness (MOE) and the use of adaptive system and other independent variables.; This study aimed to answer the following questions: (1) What performance-measure improvements can be achieved using a real-time adaptive signal control system on the subject corridor? (2) Do side street users of the system enjoy the same level of improvement compared to users traveling on the main-line?; This research showed that adaptive traffic signal control generally has a positive impact on the system; however, differences could be observed based on the direction of traffic and volume thresholds. Based on the empirical studies, average speed improved up to 32%, the travel time decreased up to 32% and number of stops decreased up to 63% under adaptive control in the eastbound direction. Westbound traffic, however, was moderately impacted...negatively! A difference between side streets and main streets was measured, although the sample from the side streets was not adequate to draw strong conclusions. |
