Mid-America Transportation Center


Date of this Version


Document Type



Report # MATC-UNL: 421 Final Report 25-1121-0001-421


Copyright 2012 Mid-America Transportation Center


Erroneous decisions by drivers to stop or go at the onset of yellow can lead to incidences of premature stopping or red light running, which in turn can cause severe rear end or right angle collisions. Because trucks or busses are relatively less maneuverable, have lower available acceleration and lower comfortable deceleration rates, and have a higher line of sight than do passenger vehicles, the risk of crashes is higher for trucks than other vehicles upon stop or go situations. Dilemma zone protection systems are used at high speed intersection s to enhance safety; however, such systems are generally designed around the dilemma zone boundaries of cars, and are static, lacking the intelligence to adapt to existing traffic, weather, or visibility conditions. The current research examined the effect of information systems such as advance warning flashers (AWFs) on the probability of conflict at onset yellow at high-speed intersections. A probit modeling technique was used to establish dilemma zone boundaries. Based on dilemma zone boundaries, probability of perceived conflict curves were computed and compared against actual conflicts that were observed at each of the studied intersections. This information was used to generate a better understanding of the risks associated with the use of AWFs. Results demonstrated that the provision of stop/go information that was consistent with the actual duration of yellow reduced the variability of driver decision making and reduced the dilemma hazard. When no information was provided to drivers, the critical time threshold for stopping was very close to the actual duration of yellow. These findings implied that drivers were inclined to stop when the time to stop bar was greater than the duration of yellow, and were inclined to go when the time to the stop bar was less than the duration of yellow. This concept was used to develop a prototype Yellow Onset Driver Assistance (YODA) system, consisting of a pole-mounted unit (StreetWave) and an in-vehicle unit (MobiWave). The in-vehicle unit was designed to request decision assistance from the pole-mounted unit as a truck approaches an intersection; based on the time to the stop bar and the duration of yellow, the YODA system advises drivers on whether or not it is safe to proceed through the intersection.