SIMULATION RESULTS & DESIGN CRITERIA - TRAFFIC SIMULATION FOR THE DESIGN OF UNIFORM SERVICE ROADS IN MOUNTAINOUS TERRAIN - VOL III

A DETAILED SIMULATION OF MULTILANE HIGHWAY FLOW HAS BEEN DEVELOPED, VALIDATED, AND APPLIED TO FLOWS OF A MIXTURE OF COMMERCIAL AND PASSENGER VEHICLES ON GRADES AND LEVEL TERRAIN. THE RESULTS ARE ANALYZED AND PRESENTED. THE ON-GRADE, OPERATING SPEED-CAPACITY RELATIONS DERIVED FROM THE SIMULATION RESULTS HAVE BEEN USED TO CONSTRUCT DESIGN GUIDES WHICH INDICATE ON-GRADE SERVICE LEVELS FOR VEHICLE MIXES (UP TO 20% COMMERCIAL) ON 4% AND 6% GRADES WITH TWO LANES ONE WAY. A PROCEDURE FOR ESTIMATING 2% ON-GRADE SERVICE LEVELS IS GIVEN. THE SIMULATION RESULTS ARE COMPARED WITH AASHO POLICY WHICH INCLUDES A PROCEDURE FOR CALCULATING GRADE-FLOW COMBINATIONS WHICH WARRANT A CLIMBING LANE (THIRD LANE ONE WAY). IT IS CONCLUDED THAT THESE GRADE-FLOW COMBINATIONS PROVIDE B' TO C' SERVICE LEVELS WITH TWO LANES ONE WAY ACCORDING TO SIMULATION RESULTS. THE SIMULATION RESULTS ARE ALSO COMPARED WITH THE HIGHWAY CAPACITY MANUAL WHICH PROVIDES A CONVENIENT GRAPHICAL METHOD TO ESTIMATE THE NEED FOR A CLIMBING LANE. FOR SHORT AND MODERATE LENGTH GRADES THE MANUAL PROCEDURE, INDICATES A CLIMBING LANE FOR FLOWS WITH SERVICE LEVELS B' AND C'. FOR LONG GRADES WITH 6% OR MORE COMMERCIALS THE MANUAL RESULTS MAY INDICATE A CLIMBING LANE FOR FLOWS WHICH HAVE A HIGH LEVEL OF SERVICE WITH JUST TWO LANES ONE WAY. MIXED FLOWS (UP TO 20% COMMERCIAL) WHICH ARE AT AASHO "DESIGN CAPACITY" IN LEVEL TERRAIN CAN OBTAIN THE EQUIVALENT "SERVICE" SPEEDS ON GRADES (UP TO 6%) WHICH HAVE A WELL DESIGNED CLIMBING LANE. THE SAME FLOW WILL ATTAIN EQUIVALENT "SERVICE" SPEED ON A 6% DOWNGRADE WITH TWO LANES ONE WAY WHERE COMMERCIALS EMPLOY CRAWL SPEED TYPICAL FOR THIS GRADE. A HIGH RISK-EXPOSURE REGION CAN DEVELOP AT THE CREST WHERE A DECELERATION WAVE IS GENERATED BY THE COMMERCIAL CRAWL SPEEDS AND ENSUING FLOW DYNAMICS. /AUTHOR/

  • Corporate Authors:

    Midwest Research Institute

    425 Volker Boulevard
    Kansas City, MO  USA  64110-2299

    Missouri State Highway Commission

    State Highway Building
    Jefferson City, MO  USA  65101

    Bureau of Public Roads /US

    400 7th Street, SW
    Washington, DC  USA  20590
  • Authors:
    • St John, A D
  • Publication Date: 1970-3-31

Subject/Index Terms

Filing Info

  • Accession Number: 00227017
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Report/Paper Numbers: CPR-11-5093
  • Files: TRIS, STATEDOT
  • Created Date: Sep 28 1970 12:00AM