Date of this Version
Intersection crashes average approximately 8,500 fatal and 900,000 injury accidents a year (1). At the onset of yellow at a high speed signalized intersection, a driver may encounter a region of the intersection approach, where they can neither stop safely nor be able to clear the intersection before the red indication. A wrong decision to stop when it would have been safer to proceed can lead to a severe rear-end collision. Conversely, a wrong decision to proceed through the intersection could lead to the driver running the red light and possibly causing a right angle collision. The traditional surrogate measure of safety, dilemma zone, denotes the region of risk but does not quantify the level of risk.
Driver’s data was collected at five high speed intersections. A probit modeling technique was used to establish dilemma zone boundaries. Results revealed the effects of providing or lack of providing information. Specifically, the results indicate the effects AWFs have on the probability of stopping and perceived conflict curves. Sites providing information through PTSWF had earlier probability of stopping curves in particular Site 2 and Site 5’s probability of stopping curves were drastically different than the other studied sites. The risk associated with being downstream of the severe deceleration distance and upstream of the maximum passing distance was calculated for a variety of speeds at each intersection. An overall weighted average was then computed and compared to the observed conflicts. An association could be seen in the comparison between the observed conflicts and the computed risks, as sites with larger severe deceleration risk had a larger proportion requiring severe deceleration and vice versa. Thus, caution should be used by engineers before providing drivers with information at a high speed intersection.