Improved perception-reaction time information for intersection sight distance

2002Final reportMorales, J. M.PDFTech ReportFHWA-RD-02-003DTFH61-84-C-00047Reaction timeVisibility distanceAutomobile driversHuman subject testingUnited States. Federal Highway AdministrationHostetter, Robert S.McGee, H. W.Crowley, K. W.Seguin, E. L.Dauber, G. W.Institute for Research (State College, Pa.)United States. Federal Highway Administration. Office of Safety and Traffic Operations Research and DevelopmentNTL-SAFETY AND SECURITY-Highway SafetyNTL-SAFETY AND SECURITY-Human FactorsFederal Highway AdministrationPerception-reaction time (PRT) data were obtained in an operational setting to assess the adequacy of existing PRT specifications for intersection sight distance standards. A sample of 124 subjects traversed a 3-hour driving circuit in an instrumented vehicle. An analysis of the YIELD-controlled (Case II) reaction data showed that the first reaction occurred before stopping sight distance in over 90 percent of the trials. On the basis of this finding and the recent finding that the PRT associated with stopping sight distance was adequate, it was concluded that the current driver time-related specifications for Case II intersections are adequate. The PRT measured for STOP-controlled (Case III) intersections was the interval from the first head movement after a stop to the application of the accelerator to enter the intersection. The mean PRT was 1.82 seconds, with the 85th percentile value being approximately 2.7 seconds. An analysis showed that the through movements produced a value lower than the overall mean and the turning movements produced a higher value. This led to the recommendation that the current value of 2.0 seconds be maintained for Case IIIA, but that the PRT for Cases IIIB and C (turning movements) be increased to 2.5 seconds. The results showed that there were no significant age or sex differences for any of the PRT measures