SLIPPERINESS OF HIGHWAY PAVEMENTS - PHASE I

THIS STUDY EVALUATED THE RELATIONSHIPS BETWEEN (1) PAVEMENT FRICTION AND TEST SPEED, (2) FRICTION LEVELS AND TRAFFIC VOLUME, AND (3) FRICTION LEVELS AND WET PAVEMENT ACCIDENTS. IT ALSO INCLUDED THE CORRELATION OF FRICTION MEASUREMENT UNITS AND THE ESTABLISHMENT OF 30 SITES FOR LONG-RANGE OBSERVATION OF FRICTION LEVELS. AT 61 SITES, STOPPING DISTANCE TESTS WERE PERFORMED SO THAT A CORRELATION COULD BE ESTABLISHED BETWEEN VALUES OBTAINED WITH A TWO-WHEEL SKID TRAILER AND THOSE OBTAINED WITH A STOPPING -DISTANCE CAR. THE REGRESSION ANALYSES PERFORMED ON THESE SETS OF DATA INDICATE THAT THE BEST PREDICTING EQUATIONS FOR STOPPING-DISTANCE NUMBERS OCCUR WHEN THE TRAILER TESTS AT 30 MPH. DATA FROM 62 SITES WERE USED TO ESTABLISH THE RELATIONSHIP BETWEEN PAVEMENT FRICTION AND TEST SPEED. IT WAS FOUND THAT THE FINE-TEXTURED PAVING MIXES WHICH ARE NORMALLY USED IN VIRGINIA ALL HAD SIMILAR SPEED GRADIENT CURVES. THE OVERALL AVERAGE GRADIENT WAS ABOUT 0.7. THIS FINDING WOULD NOT NECESSARILY BE VALID FOR OTHER TYPES OF PAVING MIXES OR DIFFERENT TEST CONDITIONS. FORTY-SIX SITES WERE TESTED TO DETERMINE THE RELATIONSHIP BETWEEN FRICTION LEVEL AND ACCUMULATED TRAFFIC VOLUME. IT WAS FOUND THAT NON- POLISHING S-4 AND S-5 BITUMINOUS MIXES HAD AN AVERAGE PSDN OF 48 AFTER 25-30 MILLION VEHICLE PASSES. NON- POLISHING PCC MIXES LOST SKID RESISTANCE MORE RAPIDLY. THEY HAD AN AVERAGE PSDN OF 44 AFTER 20-25 MILLION VEHICLE PASSES. I-2 AND I-3 BITUMINOUS MIXES WITH LIMESTONE AGGREGATES HAD THE MOST RAPID LOSS OF SKID RESISTANCE; THEIR AVERAGE PSDN WAS 42 AFTER ONLY 16 MILLION PASSES. FIVE HUNDRED AND TWENTY-ONE SECTIONS ON VIRGINIA'S INTERSTATE SYSTEM, TOTALLING 312.8 MILES, WERE STUDIED TO DETERMINE THE RELATIONSHIP BETWEEN THE PERCENT OF WET ACCIDENTS AND PREDICTED STOPPING- DISTANCE SKID NUMBERS. THE SITES WERE SEPARTED INTO FOUR CATEGORIES: OPEN ROADWAY, NON-OPEN ROADWAY, OPEN INTERCHANGES, AND NON-OPEN INTERCHANGES. IT WAS FOUND T THAT THE MINIMUM PSDN FOR THE TRAFFIC LANES OF INTERSTATE ROADWAYS WITH A MEAN TRAFFIC SPEED OF ABOUT 65-70 MPH SHOULD BE 42. /AUTHOR/