Estimating Rear-end Accident Probabilities at Signalized Intersections: A Comparison Study of Intersections With and Without Green Signal Countdown Devices

摘要

Rear-end accidents are the most common accident type at signalized intersections, since thediversity of actions taken increases due to signal change. Green signal countdown devices(GSCD), which have been widely installed in Asian countries are thought to have thepotential of improving capacity and reducing accidents, but some negative effects onintersection safety have been observed in practice, for example, an increase of rear-endaccidents.Based on the field observation and data collection at four adjacent intersections along anarterial in Suzhou, China, in which two are GSCD intersections, a total of 3350 samples oftimestamps associated with 557 vehicles have been collected. A microscopic modelingapproach has been applied to estimate the rear-end accident probability during phasetransition interval. The rear-end accident probability is determined by the probabilities: (1) aleading vehicle makes a “stop” decision, which is formulated by using a binary logistic modeland (2) the following vehicle fails to stop in the available stopping distance, which is closelyrelated to the critical deceleration used by the leading vehicle. Based on Monte-Carlosimulation results, rear-end probabilities at GSCD intersections and NGSCD intersectionshave been compared, it shows that the installation of GSCD devices creates a double-edgesword to vehicle safety and the negative effects are thought to be greater. Though GSCDdevices can reduce rear-end accident probability for vehicles that have no difficulties to makestop/go decisions when approaching the stop line during phase transition interval, theyincrease rear-end accident probability for vehicles that stop/go decision is not easy to make.Further, correlation between speeds and rear-end accidents has been investigated, the resultsreveal that too low speeds are more likely to provoke rear-end accidents at certain sections ofthe approach lane during phase transition interval.Based on the above research findings, we recommend that GSCD devices should becautiously installed and too low speed at approach lanes during phase transition intervalshould be avoided by speed management and traffic education.