Guidelines for the Installation of Left-Turn Phasing

The objective of this study was to update the guidelines to be considered when determining whether left-turn phasing should be used and the appropriate type at phasing to use. Emphasis was placed on high speed areas. There were 264 intersections included in the study with data obtained tor 518 approaches at these intersections. The data included accidents and characteristics at the intersection. Traffic conflict data were collected. Simulation models were used to estimate delays. Recommendations were made concerning guidelines to consider when deciding whether to install left turn phasing and whether to use protected-only or protected/permitted phasing. Variables considered included accident history, traffic volume and delay, traffic speed, number at left-turn lanes, number of opposing lanes, sight distance, intersection geometrics, left-turn volume, and opposing volume.