EFFECT OF TRAFFIC VOLUMES AND NUMBER OF LANES ON FREEWAY ACCIDENT RATES

THREE YEARS OF EXPERIENCE ON 659 MI OF FOUR-, SIX-, AND EIGHT-LANE FREEWAYS HAVE REVEALED THAT THE ACCIDENT RATES FOR EACH CLASSIFICATION WILL NORMALLY INCREASE WITH AN INCREASING ADT. THE RATE OF INCREASE PER 10,000-VEH INCREASE IN ADT IS FOUR-LANE, 0.240 ACCIDENTS /MVM, SIX-LANE, 0.094 ACCIDENTS/ MVM, AND EIGHT-LANE, 0.078 ACCIDENTS/ MVM. FOR ANY GIVEN ADT, THE FOUR-LANE FREEWAYS HAVE A HIGHER ACCIDENT RATE THAN THE SIX-LANE, AND SIX-LANE FREEWAYS HAVE A HIGHER RATE THAN THE EIGHT-LANE. THEREFORE, AS THE ADT INCREASES, THE DIFFERENCE IN RATES BETWEEN THE THREE CLASSIFICATIONS BECOMES GREATER. THIS RELATIONSHIP INTRODUCES THE POSSIBILITY OF SIGNIFICANTLY REDUCING THE TOTAL NUMBER OF FREEWAY ACCIDENTS BY INCREASING THE NUMBER OF TRAFFIC LANES, EVEH THOUGH THE INCREASE IS NOT REQUIRED BY TRAFFIC VOLUMES. /AUTHOR/