交通信号研究外文文献翻译中英文.docVIP

交通信号研究外文文献翻译 () 文献出处： Vehicular Technology IEEE Transactions on, 2012, 3(1):8-16. 英文原文 Traffic signals Roozemond Jean In the United States alone ,some 250,000 intersections have traffic signals , which are defined as all power-operated traffic-control devices except flashers, signs , and markings for directing or warning motorists, cyclists, or pedestrians. Signals for vehicular , bicycle , and pedestrian control are ? pretimed ? where specific times intervals are allocated to the various traffic movements and as traffic actuated where time intervals are controlled in whole or in part by traffic demand. Pretimed Traffic Signals Pretimed traffic signals are set to repeat regularly a given sequence of signal indications for stipulated time intervals through the 24-hr day. They have the advantages of having controllors of lower first cost and that they can be interconnected and coordinated to vehicles to move through a series of intersections with a minimum of stops and other delays. Also, their operation is unaffected by conditions brought on by unusual vehicle behavior such as forced stops, which , with some traffic-actuated signal installations may bring a traffic jam. Their disadvantage is that they cannot adjust to short-time variations in traffic flow and often hold vehicles from one direction when there is no traffic in the other. This results in inconvenience, and sometimes a decrease in capacity. ‘ Cycle length ’ the time required for a complete sequence of indications, ordinarily falls between 30 and 120s. Short cycle lengths are to be preferred, as the delay to standing vehicles is reduced. With short cycles, however a relatively high percentage of the total time is consumed in clearing the intersection and starting each succeeding movement. As cycle length increases, the percentage of time lost from these causes decreases. With high volumes of traffic, it may be necessary to increase the cycle length to gain added capacity. Each traffic lane of a normal s