EFFECT OF GRADES ON SERVICE VOLUME

THE PURPOSE OF THIS RESEARCH WAS TO DEVELOP A LEVEL-OF- SERVICE CHART RELATING SERVICE VOLUME TO NUMBER OF TRUCKS AND STEEPNESS AND LENGTH OF GRADES FOR RURAL FREEWAYS WITH TWO LANES IN ONE DIRECTION. TRUCK SPEED DISTRIBUTIONS OBSERVED BY TIME-LAPSE PHOTOGRAPHY METHODS ON VARIOUS GRADES IN CALIFORNIA WERE USED TO CALCULATE RELATIVE NUMBER AND DURATION OF PASSING MANEUVERS. THE PREMISE IN DEVELOPING THE LEVEL-OF-SERVICE CHART IS THAT TRAFFIC IS AFFECTED BY GRADES IN THREE WAYS' /1/ LENGTH OF GRADE. /2/ STEEPNESS OF GRADE /SPEED OF TRUCKS/, AND /3/ FREQUENCY OF TRUCKS. EVIDENCE IS GIVEN THAT QUALITY OF FLOW FOR CARS PASSING A TRUCK OR SERIES OF TRUCKS WILL NOT BE SERIOUSLY-AFFECTED IF THE CAR FLOW RATE DOES NOT EXCEED 1200 TO 1500 VPH AND ALL TRUCKS OR SLOW VEHICLES STAY IN THE RIGHT LANE ONLY. HOWEVER, ALL TRUCKS DONT STAY IN THE RIGHT LANE. A TRUCK WILL PASS ANOTHER SLOWER TRUCK AS SOON AS HE CATCHES UP, REGARDLESS OF AUTOMOBILE VOLUME LEVELS. THE NUMBER OF TRUCK-PASSING-TRUCK MANEUVERS FOR A GIVEN AVERAGE TRUCK SPEED VARIES DIRECTLY WITH /1/ THE LENGTH OF GRADE AND /2/ THE SQUARE OF THE NUMBER OF TRUCKS. THE NUMBER AND DURATION OF PASSING MANEUVERS IS RELATED TO THE SPEED DISTRIBUTION OF THE TRUCKS. FROM THE FIELD OBSERVATIONS, A FAMILY OF CURVES WAS DRAWN SHOWING AUTOMOBILE AND TRUCK VOLUME FOR A CONSTANT LEVEL OF SERVICE AS THE LENGTH AND STEEPNESS OF GRADE ARE VARIED. THE EFFECT ON OPERATION BY PROVIDING A CLIMBING LANE CAN BE ASCERTAINED. /BPR/

  • Supplemental Notes:
    • Hpr-1/2/, BPR NO. 31
  • Corporate Authors:

    California Division of Highways

    Bridge Department
    Sacramento, CA  USA  05914
  • Authors:
    • NEWMAN, L
    • Moskowitz, K
  • Publication Date: 1964-12-10

Subject/Index Terms

Filing Info

  • Accession Number: 00203109
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Files: TRIS
  • Created Date: Sep 1 1994 12:00AM