LEFT-TURN QUEUES AT UNSIGNALLIZED INTERSECTIONS

Scottsdale, Arizona allows median breaks only at intervals of 660 feet on arterial streets in order to provide storage length for left turning vehicle queues in both directions. Recently a median break was requested approximately 480 feet south of a major intersection on a 6-lane arterial. The paper describes how a procedure was developed to determine the anticipated left-turn queue at the proposed median break. The length of the left-turn storage lane could then be determined. It would then be possible to determine whether there is adequate distance to allow the left-turn storage lane and thereby the proposed median break. The relationships that need to be established in order to make this determination are described.