SAFETY AND EFFICIENCY FOR EXCLUSIVE LEFT-TURN LANES AT SIGNALIZED INTERSECTIONS

Several combinations of left-turn signal phase patterns and indication sequences exist for left-turn treatments and operations. Thus far, there have been no comprehensive guidelines to assist traffic engineers in selection of the appropriate phasing type and sequence. Often engineers rely on experience or trial-and-error until a suitable pattern is found. A study was undertaken to examine safety and efficiency of left-turn movements at signalized intersections, based on left-turn accident data in three consecutive years and the average left-turn stopped delay per vehicle in the peak-hour period. The study’s purpose was to attempt to develop models that capture potential trade-offs between left-turn efficiency and safety. The research entailed conducting statistical and traffic engineering analyses of actual field data, focusing specifically on accident and left-turn delay data for various left-turn phasing treatments. The data analyses are based on field studies of 54 intersections in Texas and Louisiana.