有无倒计时条件下黄灯第二类困境区域分布

Effects of Countdown Timer onthe Type Ⅱ Dilemma Zones

为进一步论证倒计时对黄灯第二类困境区域分布的影响,以有无倒计时信号交叉口为研究对象,利用视频观测法,采集黄灯启亮时首停车和末行车至停车线的距离和速度,分析有无倒计时条件下驾驶员行驶行为决策,应用二元Logit回归分析方法,构建有无倒计时条件下停车概率模型,确定第二类困境区域上下边界,并探讨有无倒计时条件下第二类困境区域分布。结果显示,黄灯启亮时车辆至停车线距离和倒计时增大停车概率,但黄灯启亮时车辆速度减小停车概率;倒计时条件下第二类困境区域移向停车线,但其长度仍为24.1m。因此,倒计时不能缩小黄灯第二类困境区域。然而,确定第二类困境区域边界过程中未考虑倒计时与其他变量之间的相互作用,这可能导致低估倒计时的效果,后续研究将予以改进。

Very few studies have investigated the distribution variation of the Type II dilemma zone under the condition of with and without countdown timer at intersections,and the conclusions drawn to date are controversial.The objective of this study is to further examine the effect of countdown timers on the Type II dilemma zone through videotaping vehicle movements at an unsignalized intersection.When the signal changes to yellow,the speeds and distances to the stop bar of the first vehicle stopped and the last vehicle passing through are measured and collected.Driving behavior under the two scenarios of with/without countdown timer is analyzed.A binary Logit regression is used to develop the stopping probability model under the two scenarios.The boundary of the type II dilemma zones is determined and the type II dilemma zones under the two scenarios are investigated.The results show that stopping probabilities increases when vehicles have longer distances from stop bar and/or with countdown timers;while higher vehicle speeds decrease the stopping likelihood.The Type II dilemma zones move closer to the stop line when a countdown timer is installed,but its length is still 24.1m.Therefore,countdown timers will not reduce the range of the Type II dilemma zones.However,in this study,the interaction effects of countdown timers and other variables are not considered during the process of determining the boundaries of the Type II dilemma zones,which will probably lead to underestimating the effectiveness of countdown timers.