LEFT-TURN SIGNAL PHASING FOR FULL-ACTUATED SIGNAL CONTROL

Many warrants and guidelines exist concerning left-turn phasing at signalized intersections. However, there is still a lack of understanding about the left-turn phasing requirements for full-actuated signal control. Using computer simulation, a knowledge base is developed to assist in the choice between permissive phasing and protected/permissive phasing for this type of signal control. The important factors concerning such a choice include left-turn volume, opposing volume, the number of opposing lanes, length of left-turn bay, and the volume of cross traffic. The collective impact of these factors on left-turn phasing cannot be adequately assessed through the use of simple rules of thumb. The lengths of left-turn bays that allow protected/permissive phasing to be effectively used are also identified.