Right turn on red (RTOR) is permitted at signalised intersection in the United States. Adequate intersection sight distances should be provided to ensure that the RTOR drivers turn into receiving lanes safely and efficiently. However, in practice it is not unusual to find signalised intersections with restricted right-turn sight distances, at which RTOR is still permitted. This research is focused on investigating if restricted right-turn sight distances have a significant impact on RTOR behaviours. A pilot field observation study was conducted at four signalised intersections: two with restricted right-turn sight distances and two with sufficient sight distances for 25 mph and 35 mph speed limits, respectively. Using a video camera, both gap-acceptance and non-gap-acceptance RTOR behaviour data were collected at the intersections. In comparisons of RTOR behaviours at intersections with and without sight-distance problems, it was found that a restricted sight distance can cause drivers to seriously encroach into pedestrian crossings in order to maximize available sight distances at the intersections; lead to a higher non-stop RTOR violation rate; cause drivers to accept smaller gaps; and increase the possibility of conflicting with pedestrians. Due to these significantly negative effects on RTOR behaviours, traffic engineers are appealed to pay more attention to the right-turn sight distance issue at signalised intersections. (Author/publisher)
Abstract