RELATIONSHIP OF RURAL HIGHWAY GEOMETRY TO ACCIDENT RATES IN LOUISIANA

A STUDY WAS CONDUCTED TO: (1) DETERMINE WHICH GEOMETRIC VARIABLES CONTRIBUTE MOST TO ACCIDENTS, AND (2) PREDICT THE ACCIDENT POTENTIAL OF A CERTAIN SECTION OF LOUISIANA HIGHWAYS. THIS STUDY INVOLVED APPROXIMATELY 1,000 MILES OF RURAL HIGHWAYS DISTRIBUTED EVENLY THROUGHOUT LOUISIANA. THE ACCIDENT RECORDS INVESTIGATED COVER A 5-YEAR PERIOD FROM 1962 TO 1966. THE VARIABLES STUDIED, IN ORDER TO FIND THEIR RELATION TO ACCIDENTS, WERE PERCENTAGE OF TRUCKS, TRAFFIC RATIO, LANE WIDTH, SHOULDER WIDTH, PAVEMENT CROSS SLOPE, HORIZONTAL ALIGNMENT, VERTICAL ALIGNMENT, PERCENTAGE OF CONTINUOUS OBSTRUCTIONS, MARGINAL OBSTRUCTIONS PER MILE, AND TRAFFIC ACCESS POINTS PER MILE. THESE 10 VARIABLES, THEIR SQUARES, AND THEIR FIRST ORDER INTERACTIONS WERE USED IN A REGRESSION ANALYSIS TO CONSTRUCT MATHEMATICAL MODELS TO DETERMINE THE CONTRIBUTION OF THE VARIABLES TO TOTAL ACCIDENTS, ACCIDENTS ON WET ROADS, ACCIDENTS ON DRY ROADS, ACCIDENTS DURING THE DAY, ACCIDENTS DURING THE NIGHT, TOTAL INJURIES, AND TOTAL FATALITIES. ONE MATHEMATICAL MODEL SHOWS THAT A TOTAL OF APPROXIMATELY 46 PERCENT OF ALL ACCIDENTS ARE EXPLAINED BY THE 10 VARIABLES INCLUDED IN THIS STUDY. THE VARIABLES NOT INVESTIGATED-INVOLVING THE DRIVER, THE VEHICLE, AND OTHER GEOMETRICS-ACCOUNT FOR THE REMAINDER OF THE VARIATION IN TOTAL ACCIDENTS. BASED ON THEIR INTERACTION WITH TRAFFIC VOLUME, THE 2 GEOMETRIC VARIABLES HAVING THE MOST IMPORTANT EFFECT ON ACCIDENT RATES ARE PAVEMENT CROSS SLOPE AND TRAFFIC CONFLICTS. THE REMAINING GEOMETRIC VARIABLES STUDIED IN ORDER OF DECREASING EFFECT ON ACCIDENT RATES ARE LANE WIDTH, HORIZONTAL ALIGNMENT, AND SHOULDER WIDTH. /AUTHOR/