UTILIZATION AND TIMING OF SIGNAL CHANGE INTERVAL

The problem of timing the signal change interval has received increased attention in recent years. Much of this attention is focused on two issues: whether a constant yellow interval should be used and whether the timing equations suggested by the Institute of Transportation Engineers (ITE) can realistically reflect driver needs for the change interval. These two issues are examined on the basis of observed driver behavior. The 95th percentile yellow interval requirements are found to vary from 3 to 5 sec. Such requirements do not have a positive linear correlation with the approach speed. The 85th and 95th total change interval requirements have strong linear correlations with vehicle clearance time. The ITE's timing equations should be replaced by simpler ones that can better explain driver behavior.