DECELERATION LEVELS AND CLEARANCE TIMES ASSOCIATED WITH THE AMBER PHASE OF TRAFFIC SIGNALS

OBSERVATIONAL WORK CARRIED OUT AT TWO DIFFERENT INTERSECTIONS SUGGESTS THAT AMBER PERIODS OF ABOUT 5.5 SECONDS ARE REALISTIC IN THAT SUCH AMBER DURATIONS PROVIDE A 'CLEARING TIME' THAT ALLOWS ALL OR NEARLY ALL MOTORISTS TO CLEAR AN INTERSECTION. THE PROBABILITY OF STOPPING IS ZERO WHEN THE TIME TO CLEAR THE INTERSECTION IS ABOUT 0.5 SEC LONGER THAN THE AMBER PHASE. THE DATA ON STOPPING AS A FUNCTION OF DECELERATION REQUIRED TO STOP SHOWS DRIVERS TO BE MORE CONSISTENT THAN MIGHT HAVE BEEN ANTICIPATED. THESE RESULTS INDICATE THAT FOR BOTH INTERSECTIONS STUDIED, DRIVERS WERE VIRTUALLY CERTAIN TO STOP IF THEIR REQUIRED DECELERATION WAS LESS THAN 8 FT/SEC SQ, AND VIRTUALLY CERTAIN TO CONTINUE IF THE DECELERATIONS REQUIRED WERE IN EXCESS OF 12 FT/SEC SQ. /AUTHOR/