Effect of green phase countdown timer on reduction of drivers' dilemma at signalized intersection

This study numerically evaluated the effect of green phase countdown timer (CDT) on the reduction of driver's dilemma at signalized intersection. The proposed system provides the remaining green time to the drivers in real-time to support the stop or pass decision-making. Driving simulator experiment equipped with the CDT indication system was carried out to collect the drivers' data when approaching to a signalized intersection. It was confirmed that the CDT encouraged most drivers to reduce their approaching speed and to prevent falling into the dilemma zone. A logistic regression analysis (LRA) showed that the remaining distance and acceleration rate significantly contributed to their decision making after amber onset. Especially, it contributed to decreasing the approaching velocity for the drivers who travels at high speed. Also, the intent estimation was carried out using the LRA to infer whether they stop or pass the intersection. Most of the drivers aided by the assistance system terminated their decision much earlier far from the stop line. It was concluded that the CDT was quite effective in reducing drivers' approaching speed and preventing falling into the dilemma zone in most cases. Also, it contributes to shift their stop/pass decision much earlier to safely stop or pass the intersection without any confusion.