The effectiveness of daytime running lamps, DRLs, for passenger cars, are examined using three different crash types, two vehicle different direction fatal crashes, two vehicle non-fatal crashes, and single vehicle fatal pedestrian crashes. Two statistical techniques, the odds ratio and simple odds techniques were used to analyse the data. An increase of 8 percent in daytime two vehicle opposite direction fatal crashes, for vehicles equipped with DRLS, is observed using the odds ratio technique. A decrease of 2 percent in daytime two vehicle opposite direction fatal crashes, for vehicles equipped with DRLS, is obtained using the simple odds technique. Neither result is statistically significant. Non-fatal two vehicle crashes from Florida, Maryland, Missouri, and Pennsylvania are also examined. Data from these states estimate that DRLs reduce daytime non-fatal two vehicle crashes by 5 to 7 percent depending on the statistical technique used. The 7 percent reduction of daytime non-fatal two vehicle crashes using the simple odds technique is statistically significant at the p=0.05 level. DRLs reduced daytime fatal single vehicle pedestrian deaths by 28 to 29 percent depending on the statistical technique used. The reduction of 28 percent using the simple odds technique is statistically significant at the p=0.05 level. A case-control method was chosen as the approach for this study, since only specific make-models for each year were equipped with DRLs. The number of crashes for a set of vehicles equipped with DRLs is compared to either a group of similar vehicles without DRLs produced in earlier years or a fleet of vehicles without DRLs produced by a different manufacturer, namely Ford, built in the same years. Both comparison groups of vehicles are analysed by time of day and crash type. Two independent statistical techniques, the odds ratio an the simple odds, were use to analyse the data. Both techniques attempt to control for factors, other than the presence or absence of DRLs, that could be associated with crash occurrence. Individual estimates are combined using the methods described in Fleiss (1981) to obtain stable statistically significant results. (Author/publisher)
Abstract