UC Irvine

For most signalized intersections, left-turn movements are considered as a primary contributor to intersection delay. The concept of eliminating left-turn movements is now feasible with the rise of GPS-based routing which will allow the active routing of vehicles in networks with reduced left turns. This research seeks to estimate the impact of left turn reductions on overall travel time and left turn delay at intersections.

The research objective is to evaluate the effect of left turn movement elimination in sample networks. The type of intersections considered is restricted to a grid network but is defined by the roadway hierarchy. A sample network was selected based on a real world network and reflecting observed volumes, travel times, and delays. The analysis approach is to eliminate left turn movements in three types of intersections by applying turn prohibitions and adjusting cycle lengths and turn penalties on other movements. Network performance is then assessed based on delay reduction, total travel time, and fuel consumption. It was concluded that selective reduction of left turn movements can improve network performance.