Safety effects of limited stopping sight distance on crest vertical curves

Previous studies that examined the relationship between stopping sight distance and safety have been inconclusive and inconsistent; however, the fact that a relationship has not been established does not necessarily imply that stopping sight distance is not a contributing factor in some crashes. Instead, it means that existing databases have failed to quantify any relationship that might exist. A promising approach to identifying such a relationship is a detailed examination or case study of crashes from a relatively large sample of limited sight distance roadways. If limited sight distance is a factor that contributes to crashes, it should show up in such a study. The objective of this study was to determine whether stopping sight distance was a contributing factor in crashes on roadway segments with limited sight distance crest vertical curves. This objective was accomplished by reviewing 439 narratives from crashes that occurred on 33 multilane and two-lane roadways with limited sight distance crest vertical curves. The findings suggest that the crash rates on rural two-lane highways with limited stopping sight distance are similar to the crash rates on all two-lane rural highways. They also suggest that the percentage of accidents involving large trucks and older drivers is similar on limited sight distance highways and all two-lane rural highways. Thus, for the range of conditions studied, limited stopping sight distance does not appear to be a safety problem.