Evaluation of association between observed driving speeds and the occurrence of crashes using naturalistic driving study data

Abstract

The SHRP2 Naturalistic Driving Study (NDS) data were used to investigate association between actual driving speeds before known crashes and at other times. Associations were evaluated for the same driver at a location where a crash occurred and similar locations where crashes did not occur, relative to the speeds of other drivers at those locations. It was found that an increase in the speed differential relative to other drivers at the same location between 6 and 10 s before a crash occurred was significantly associated with a crash occurring. The quantile of the average speed over that five-second period served as a better predictor than the quantile of the maximum speed. Crashes were also more associated with road locations classified as limited access highways, minor arterials, and major collectors. These findings are consistent across different drivers and types of road locations. The best-performing model classified all of the crashes in the dataset perfectly, and less than half of the cases classified as crashes were not crashes. This suggests an ability to identify conditions that are at least 50 percent likely to result in a crash. The results could be used by road agencies to identify observed vehicle speed variations that are likely to result in crashes, as well as by vehicle manufacturers to develop algorithms for identifying high-risk conditions for crashes considering speeds of other vehicles in the vicinity.