A Study of Clearance Intervals, Flashing Operation, and Left-Turn Phasing at Traffic Signals. Volume 1. Summary Report

摘要

This volume is a summary of three research studies on several aspects of traffic control to improve traffic operations and reduce accidents. The first study dealt with clearance intervals and more specifically with the effectiveness of a uniform yellow interval and all-red intervals. The second study addressed the question of whether traffic signals should be put on flashing operation during low volume periods. The third study considered signal phasing that allows vehicles to make left turns during both a protected (green arrow) interval and an unprotected (green) ball) interval. Each study used a literature review, a review of state laws, questionnaires to public officials and to drivers, analytical models of traffic flow, and field studies to arrive at the recommendations.