EFFECT OF TRUCKS ON THE URBAN FREEWAY

AN INVESTIGATION WAS MADE INTO THE EFFECT OF TRUCKS OR GRADES OR BOTH ON URBAN FREEWAY LEVEL OF SERVICE. THE PRIMARY PARAMETER USED WAS ACCELERATION NOISE, A WELL-KNOWN AND WIDELY USED TRAFFIC RESEARCH PARAMETER. A TRAFFIC STREAM COMPOSED OF BOTH CARS AND TRUCKS WAS EXAMINED. A SHORT SECTION OF THE ROADWAY WAS CONSIDERED AND THE ENTERING AND LEAVING ENERGY OF THE STREAM EQUATED. ASSUMPTIONS CONCERNING THE RESISTANCE TO BOTH MOTION AND ACCELERATION WERE ALSO DEVELOPED. FOR VERIFICATION OF THE MODEL DEVELOPED, AERIAL TIME-LAPSE PHOTOGRAPHS SUPPLIED THE BULK OF THE DATA. UTILIZING 100-FT SECTIONS MARKED OFF ON THE FREEWAY SHOULDER, SPEEDS AND ACCELERATIONS FOR EACH VEHICLE PHOTOGRAPHED WERE CALCULATED. FROM THESE, MACROSCOPIC SPEED AND ACCELERATION NOISE PROFILES WERE DETERMINED. THE RESULTS OF THE RESEARCH INDICATE THAT ACCELERATION NOISE DEFINITELY INCREASES ON A POSITIVE GRADE OF A ROLLING URBAN FREEWAY. THE AMOUNT OF CHANGE IS INDEPENDENT OF THE LANE STUDIED, HOWEVER. BECAUSE OF A WIDE VARIANCE IN THE PERCENTAGE OF TRUCKS ON THE DIFFERENT LANES, THE CONCLUSION IS THAT TRUCKS DO NOT AFFECT THE OVERALL NOISE VALUES UNDER THE CONDITIONS STUDIED. THIS CONCLUSION WAS STRENGTHENED BY MICROSCOPIC NOISE VALUES AND BY AN EXAMINATION OF TYPICAL TIME-SPACE DIAGRAMS. FINALLY, CONCLUSIONS WERE MADE CONCERNING THE TYPE OF PARAMETER NEEDED TO ASCERTAIN THE EFFECT OF TRUCKS ON THE ROAD USER. /AUTHOR/