Safety Effects Of Time-reminder Strategies Before Amber Based On Drivers’ Decision-making Process

Abstract:The safety level of signalized intersections is significantly influenced by drivers’decision-making when they approach intersections with different signal devices. Both domestic and international researches of safety performances of signal devices mainly focus on doing large numbers of statistical analysis rather than exploring the mechanism of how signal devices affecting intersection safety level. This study aims to find out how the three typical green signal devices, i.e., the ones with common green-amber-red lights, with flashing green, and with green countdown respectively, affect drivers’decision-making process through their different time-reminder strategies before amber and then evaluate the safety performance of intersections with those signal types.This research scrutinized the driver-signal interaction process by establishing the underlying relationship of signal status-pre-amber decision making-dilemma zone (DZ)-at-amber go/stop decision-red light running (RLR) propensity during the phases of signal shifting. Based the decision-making process, a decision-making model has been built and verified by using artificial neural network. A comprehensive case-control field study was undertaken to verify the proposed process at six intersections, with two for each signal type. A series of binary Logistic models on driver behaviors at different phases were developed to evaluate the safety effects of different signal types. Results showed that RLR risk is not only dependent on the amount of vehicles in DZs but also substantially on the go/stop decision of those vehicles in DZs, both of which were found to be significantly affected by the device types in consideration. Specifically, both green countdown and green flashing can reduce the probability of vehicles involved in DZ presumably by informing the green time left in advance. The RLR propensity for those vehicles in DZs is increased under green countdown. But as a whole, the integrated RLR risk is the lowest at the observed sites with countdown timer.31Figures,20tables and62references.