Summary report on yellow and red intervals to improve signal timing plans for left-turn movement.

Signal intervals have long been used at intersections for clearing one traffic movement before allowing another conflicting movement to proceed. Among the signal intervals, a yellow change interval, the yellow signal period, is adopted for a driver approaching the intersection to make the decision to either stop or proceed into the intersection after the green signal turns to yellow. A red clearance interval, the all red signal period, is used to clear the intersection before the green signal for the conflicting traffic movement starts. (Author/publisher)