Perception-braking response time of unalerted drivers at signalized intersections

A study was conducted to investigate the behavior of unaltered drivers responding to a change of the signal indication at road intersections. It was demonstrated that the distribution of driver-response time for braking action, known as the brake reaction time (BRT) was an essential design parameter in traffic engineering applications. The BRT was the time interval from the moment that a driver recognized the existence of an object or hazard on the roadway ahead to the moment that the driver actually applied the brake. Driver PBRT values were determined empirically to establish a statistical distribution, while the influences of selected factors on PBRT was examined. The PBRT data were analyzed by vehicle type, vehicle initial speed and position, and presence or absence of surveillance cameras. Exploratory analysis revealed that PBRT was sensitive to vehicle position and distance in which PBRT values were higher and more variable at low initial approach speed.