A Dilemma Zone (DZ) is an invisible zone where drivers
face difficulty in choosing whether to continue or stop when
approaching an intersection at the onset of yellow. A vehicle in
the zone is in danger, because if the driver continues, the
vehicle may still be in the intersection when the signal turns
red, possibly placing it in conflict with vehicles coming from
the another direction and possibly resulting in a right-angle
collision. However, if the driver stops, the vehicle behind it
may continue, possibly leading to a rear-end collision. In this
work, a DZ’s boundary is defined by a Time to Intersection
(TTI) of between 2 s and 5.5 s. The number of vehicles in DZ
is a common used measure of safety. The greater the number of
vehicles caught in DZ, more dangerous the system is.