Abstract
In China, around ninety percent of the traffic accidents at signalized intersections occur within the signal change intervals, especially during signal change from green to red. Hence, intergreen time (IGT), that is, yellow change interval plus red clearance interval, is of great significance to the safety at signalized intersections. The conventional calculation method of IGT ignores the randomness of drivers’ behaviors, which we believe is an important factor in calculation of IGT. Therefore, the purpose of this research is to investigate a new approach to calculate the IGT based on safety reliability theory. Firstly, a comprehensive literature review concerning the conventional calculation methods of IGT is conducted. Secondly, a theoretical calculation method of IGT based on safety reliability theory is put forward; different from the conventional methods, this model accounts for the uncertainty of driving behavior parameters. Thirdly, a Monte-Carlo simulation is employed to simulate the interactive process of perception-reaction time (PRT) and vehicular deceleration and solve the proposed model. Finally, according to the Monte-Carlo simulation results, the curve clusters describing the relationship between IGT, safety reliability (50%-90%), and intersection width (15-35m) are drawn. Results show that the IGT of a signalized intersection, obeying the normal distribution, is influenced by multiple factors and most sensitive to the PRT and vehicular deceleration. Our method thus successfully incorporates the probabilistic nature of driving behavior. Taking the safety reliability into consideration can provide a more reasonable method to calculate the IGT of signalized intersections.
Highlights
China still maintains a relatively poor traffic safety record
The input and output data of the Monte-Carlo simulation are shown in Table 2, and 100,000 values of intergreen time (IGT) can be obtained by this Monte-Carlo simulation
We proposed an engineering-oriented calculation method for IGT of signalized intersections with the consideration of safety reliability
Summary
China still maintains a relatively poor traffic safety record. A study [2] showed that 16∼22% of China’s traffic accidents occurred in the urban-road intersections, and 90% of the above accidents happened within the signal change interval, especially during the change of signal lights from green to red. Calculating the intergreen time (IGT) of signalized intersections more reasonably is crucial to enhance the safety at signalized intersections. IGT is designed to avoid traffic conflicts during the signal change interval and in general equals yellow change interval plus red clearance interval [3]. To enhance the safety of signalized intersections, a relatively longer IGT is needed; this may lead to an increase in lost time and a decrease in efficiency
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