چكيده به لاتين
Intersections are one of the most vulnerable and hazardous elements of urban traffic networks. Establishing a safe intersection performance method has always been a major concern of researchers and authorities of all around the world. Installing count-down timers, which show the remained time of each phase, is one of the measures taken for solving this problem. The main purpose of using these count-down timers has been to help drivers make a proper decision about crossing the intersection or stopping before the stop line especially at the end of green phase and initial moments of amber phase, according to the information given to them. But the question is that did the count-down timers successfully do that? According to the results of recent studies of all around the world, in some cases count-down timers not only didn’t enhance the intersection safety but also endangered it. In this study, it is tried to evaluate the effect of count-down timers on intersection safety. Four different executive scenarios of timers operation have been designed and separately executed at one intersection in Arak city. Surrogate safety indexes have been used in this safety study instead of crash statistics of the site. These indexes are yellow cross, red cross, sudden brake, stop after stop line and early start. Data used in this study have been gathered by reviewing recorded films of intersection during the execution of each scenario. Then these data have been investigated by using chai-square and statistical t-tests to evaluate the effectiveness of each scenario on enhancing intersection safety.
Unlike prior studies which investigated count-down timers in simultaneously activated or deactivated manners, in this study, the individual operation of each count-down timer has also been taken into account. One of the results of this study is that for having a safer operating intersection, it is recommended to utilize the Green Signal Count-down Device (GSCD) while the Red Signal Count-down Device (RSCD) is deactivated. According to the results, all surrogate safety indexes have a better status in this situation and so the intersection operation is much safer.
Keywords: Count-down Timers, Intersection Safety, Surrogate Safety Indexes
