Intersection operational performance is highly influenced by the intersection geometric features. This fact can be demonstrated in the operations of non-traditional intersections such as triple left-turn lanes intersections. Triple left-turn lanes intersections are designed to combat high left-turn demand in a signalized area, predominantly in urban intersections. The existence of different geometric features at different triple left-turn intersections causes different magnitudes of saturation flows among the intersections. This paper discusses the study that was conducted to determine the influence of different geometric features on the operations of triple left-turn lanes. The geometric features studied include the skewness of the left-turn angle, the approach slope, the type of street--one way versus two ways, and lane type--innermost, middle and outermost lanes. Other features studied were curvature of the approach lanes, shadowing effect and intersection type--four legs versus T-intersection. Field data were collected at 15 triple left-turn intersections in Florida. Four traffic measures were used to quantify the effects of the mentioned geometric features--saturation flows, lane utilization factors, lane usage factors and left-turn factors. The results indicate that the approach grade, intersection skewness and the type of street highly influence the operational performance of triple left-turn lanes. Intersection type and lane type did not significantly influence the operation of triple left-turn lanes.
Abstract