WET-WEATHER SPEED ZONING

SPEED IS A SIGNIFICANT FACTOR IN MANY WET-WEATHER SKIDDING ACCIDENTS. ESTABLISHING WET-WEATHER SPEED LIMITS AT CERTAIN LOCATIONS, THEREFORE, MAY BE ONE WAY TO REDUCE THESE ACCIDENTS. THIS PAPER ASSIMILATES FINDINGS FROM VARIOUS SKID-RESEARCH EFFORTS TO FORM A BASIS FOR EQUATING THE AVAILABLE FRICTION AT A SITE (PAVEMENT SKID RESISTANCE) TO THE EXPECTED FRICTION DEMAND FOR SELECTED MANEUVERS. FRICTION NORMALLY DECREASES AS SPEED INCREASES. BECAUSE THE SPEEDS IN QUESTION ARE USUALLY HIGHER THAN 40 MPH, THE STANDARD SPEED AT WHICH THE SKID NUMBER IS DETERMINED, THE CHANGE IN AVAILABLE FRICTION WITH RESPECT TO SPEED MUST BE CONSIDERED. METHODS TO ACCOMPLISH THIS ARE DISCUSSED. THE PAPER PRESENTS CURVES TO DETERMINE, FOR VARIOUS PAVEMENT FRICTIONS, THE CRITICAL SPEED FOR HYDROPLANING, STOPPING MANEUVERS, CORNERING MANEUVERS, PASSING MANEUVERS, EMERGENCY PATH-CORRECTION MANEUVERS, AND COMBINED MANEUVERS. A DESIGN PROCESS TO ESTABLISH THE WET-WEATHER SPEED LIMIT IS DISCUSSED, AND EXAMPLES ARE PRESENTED TO ILLUSTRATE THE USE OF THE CURVES.