Date of this Version
NDOR Research Project Number SPR-P1(03) P554
The objective of this research project was to evaluate the effectiveness of offset opposing left-turn lanes at signalized intersections in reducing the frequency and severity of left-turn related accidents. The Cities of Lincoln and Omaha offset opposing left-turns by widening leftturn lane lines in June 1999 at six intersections. The research team investigated traffic accident patterns between January 1994 and December 2002 at those six intersections by making comparisons with two control intersections (i.e. intersections at which left-turns were not offset by lane line widening) using a four-step research methodology. First, existing literature was reviewed to determine the extent and availability of materials relevant to this project. Second, accident data were collected for the six study and two control intersections. The third step involved the analysis of the collected data. Four analysis techniques were employed to assess the effectiveness of off-setting opposing left- turn lanes by using wider left-turn lanes lines.
The research team recommends continuation of the practice of off-setting opposing left-turn lanes, where feasible. For future research, the team recommends that additional factors (e.g., number of days with adverse weather in the ‘before’ and ‘after’ periods, construction activities at or near study locations, etc.) besides traffic must also be accounted for in the analysis.