MACROTEXTURE MEASUREMENT AND RELATED SKID RESISTANCE AT SPEEDS FROM 20 TO 60 MILES PER HOUR

MACROTEXTURE IS ONE OF THE MANY VARIABLES AFFECTING THE INTERACTION AT THE TIRE-PAVEMENT INTERFACE; HOWEVER, AT PRESENT ITS RELATIVE IMPORTANCE IS QUESTIONED. FRICTION TESTS OBTAINED AT 20, 40, AND 60 MPH WITH THE TEXAS HIGHWAY DEPARTMENT RESEARCH SKID TRAILER AND MACROTEXTURE TESTS UTILIZING 4 DIFFERENT METHODS WERE CONDUCTED ON 41 PAVEMENT SURFACES. THESE SURFACES EXHIBITED WIDELY DIFFERENT FRICTION LEVELS, FRICTION-SPEED GRADIENTS, DRAINAGE CAPABILITIES, MINERALOGICAL PROPERTIES, AND TEXTURE CLASSIFICATIONS. MACROTEXTURE VALUES OBTAINED WITH THE 4 METHODS ARE COMPARED. THE EFFECTS OF MACROTEXTURE TYPES AND MAGNITUDES ON FRICTION NUMBERS AND FRICTION-SPEED GRADIENTS ARE STATISTICALLY ANALYZED AND PLOTTED. BRIEF DESCRIPTIONS OF SEVERAL MACROTEXTURE MEASUREMENT METHODS USED BY AGENCIES IN THE UNITED STATES AND OTHER COUNTRIES ARE PRESENTED. FOR THE TREADED-TIRE AND 0.020-IN. WATER-FILM THICKNESSES USED IN THIS STUDY, MACROTEXTURE WAS FOUND TO HAVE LITTLE EFFECT ON FRICTION LEVEL, BUT DID APPRECIABLY INFLUENCE THE PERCENTAGE DECREASE IN FRICTION WITH SPEED. /AUTHOR/