U‐turns are treated as left‐turns in the current procedures for estimating saturation flow rates at signalized intersections. While U‐turning vehicles are usually mixed with left‐turning vehicles in inside or left‐turn lanes and conflict with opposing through traffic as left‐turning vehicles, the vehicle operating characteristics are different. The objective of this paper is to investigate the effects of U‐turns on the traffic flow in left‐turn lanes. Field data of 600 headways of left‐turning passenger cars and 160 headways of U‐turning passenger cars are recorded. The average headways of U‐turning passenger cars are found to be significantly larger than those of left‐turning passenger cars. The effects of U‐turning vehicles depend upon the percent of U‐turning vehicles in the left‐turn lane, as well as the order of formation in the traffic stream. Adjustment factors for varying percents of U‐turning vehicles in left‐turn lanes are established.
No takes yet. Share an insight, caveat, or question.
Tsao et al. (1995) studied this question.