Abstract
Geometrical features of intersections, such as T-intersections and four-leg intersections, can give rise to several conflict points at those intersections. Without proper control at such conflict points, accidents can occur. In Thailand, the application of intelligent transportation system (ITS) technology for improvement of traffic flow and road safety is still in its infancy. This paper describes one of the pioneering uses of ITS technology to mitigate congestion and reduce accidents at intersections. The intersections under study are located in suburban Bangkok, Thailand, where major accidents have occurred as a result of red light running and speeding. Through the use of accident analysis modeling and ITS technology, it is possible to improve traffic flow and reduce the number of crashes. ITS technology, including an image-sensing concept for adaptive synchronization (green wave), was used to detect headway, spacing, number of speeding vehicles, angle of lane changing, and number of vehicles changing lanes. In particular, the image-sensing concept of traffic classified counting was used to calculate and evaluate signal phasing and cycle times for adaptive synchronization. In this operation, two closed-circuit television cameras and electronic equipment installed at each intersection were used to track vehicles passing through virtual loops, similar to the way in which induction loops in pavement detect vehicles. A variable message sign was used to flash a warning to errant drivers. After the implementation of this locally developed ITS technology, traffic flow improved significantly and the number of accidents caused by red light running and speeding decreased drastically.
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