An observational study is described in which modern digital video technology was used to obtain empirical values of driver perception-response time (PRT) for braking action at signalised junctions during the signal change interval. The PRT was examined for first stopping vehicles on straight-through movements operating under a standard 3-second amber indication and a brief all-red indication. Data were collected during daytime, dry weather conditions at five cross-junction approaches, including two approaches with traffic red-light surveillance cameras. The PRT value was found to be sensitive to the vehicle's initial position and speed, but it was not significantly influenced by camera installation and vehicle type. The overall sample of 334 first stopping vehicles gave the following PRT values: a 15th percentile value of 0.68 seconds, a mean of 1.02 seconds and an 85th percentile value of 1.28 seconds. The corresponding statistics for a subset of 132 first stopping vehicles within a transitional zone were 0.58 seconds, 0.82 seconds, and 1.02 seconds, respectively. The empirically observed 85th percentile value of 1.02 seconds compares closely with the normative design value of 1.0 second. The presence of the surveillance cameras, though not having a significant influence on PRT value, did result in increased stopping propensity during the signal change interval. (a).
Samenvatting