Investigating Positive and Negative Utilities of Red Light Cameras through a Binary Probit Analysis

Driver behavior at intersections equipped with a Red Light Camera (RLC) are influenced by many factors, including the fear of being fined for crossing the intersection during the red signal. This behavioral change may lead to the tendency of stopping at the intersection at the onset of the yellow interval. The following scenarios may arise due to this tendency: (1) the stopped driver may have a rear-end collision by a fast approaching vehicle; (2) the excessive “safe” stoppage by vehicles during the yellow interval may reduce the intersection capacity, thereby increasing congestion; and (3) the safe stoppage during yellow interval may result in reduced intersection related accidents, thereby improving intersection safety. While the first two scenarios can be seen as disutilities (or negative measures) associated with the real intent of RLCs the third scenario is the only utility (or positive measure) that is ideally considered as the basis for RLC installation. With an increasing number of RLCs along busy intersections with the standard assumption of scenario 3 above while the possibilities of scenarios 1 and 2 cannot be ruled out, it is important to thoroughly investigate positive` and negative aspects of a RLC. This can be achieved by collecting reasonably sufficient relevant field data at intersections with and without RLCs and developing a binary choice model to analyze the driver’s dilemma (or indecision) of stop and/or go during the yellow interval. The existence of an indecision zone or Dilemma Zone (DZ) can be estimated using dilemma zone curves developed from the probability of stopping vs. distance from stop bar at the onset of the yellow interval. The construction of dilemma zones can help understand the driver behavioral characteristics contributing to positive and negative aspects of RLCs. In this paper, using field data from Baltimore at 10 intersection pairs with and without RLCs that have similar geometric and traffic characteristics, the authors develop a binary probit choice model to examine driver behavior at RLCs. The results indicate that the negative utilities of RLCs may outweigh their positive utilities.