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Mid-America Transportation Center

Heavy Vehicle Adjustment Factors for High Percentages of Trucks


Researchers

  • Principal Investigator: Elizabeth Jones (ejones1@unl.edu (402) 554-3869)
  • Graduate Students
  • Chung-Jen Hsu
  • lan Xiang
  • Chung-Jen Hsu
  • lan Xiang
  • Project Status
    In Progress
    About this Project
    Brief Project Description & Background
    The most common reference for analyzing the operational characteristics of multilane highways and freeways is the Highway Capacity Manual (HCM). The general procedure used by the 2000 HCM to account for heavy vehicles is to use a heavy vehicle adjustment factor that converts heavy vehicles to passenger-car equivalents. In the 2000 HCM, this heavy vehicle adjustment factor, fHV, is independent of the percentage of heavy vehicles for extended highway and freeway segments. It varies by percent of heavy vehicles for specific grades but the tables in the 2000 HCM only provide analysis guidance for heavy vehicle percentages of 25% or less. Nebraska's highways carry a significant portion of heavy vehicle (trucks, buses and RVs) traffic. The NDOR 2004 Statewide Traffic Flow Map indicates that on I-80 alone, the percentage of AADT represented by heavy commercial vehicles is more than 25% from Lincoln to the Wyoming border. Just west of the I-80/I-76 junction on I-80, this percentage reaches a maximum of 60.9%. The objective of this research is to quantify the impact of heavy vehicles on multilane highway and/or freeways for heavy vehicle percentages of greater than 25%.
    Research Objective
    The objective of this research is to quantify the impact of heavy vehicles on multilane highway and/or freeways for heavy vehicle percentages of greater than 25%.
    Potential Benefits
    The expected benefit is more accurate reporting of levels of service and performance measures for multilane highways and freeways that have percentages of heavy vehicles in excess of 25%.
    Abstract
    Rural highways can carry a significant portion of heavy vehicle traffic as a percentage of the total traffic. Nebraska's highways serve as a good example. The Nebraska Department of Roads (NDOR) 2004 Statewide Traffic Flow Map indicates that on I-80 alone, the percentage of AADT represented by heavy commercial vehicles is more than 25% from Lincoln to the Wyoming border. Just west of the I-80/I-76 junction on I-80, this percentage reaches a maximum of 60.9%. The most common reference for analyzing the operational characteristics of multilane highways and freeways is the Highway Capacity Manual (HCM). The general procedure used by the 2000 HCM to account for heavy vehicles is to use a heavy vehicle adjustment factor that converts heavy vehicles to passenger-car equivalents. In the 2000 HCM, this heavy vehicle adjustment factor, fHV, is independent of the percentage of heavy vehicles for extended highway and freeway segments. It varies by percent of heavy vehicles for specific grades but the tables in the 2000 HCM only provide analysis guidance for heavy vehicle percentages of 25% or less. These same factors are also used in freeway facility analysis, freeway weaving analysis, and ramps and ramp junction analysis. With increasing numbers of trucks on the nation's roadways, the impact of trucks has become a more significant factor in performance and level of service analysis. The HCM performance measures and methodologies may be incorrectly reporting levels of service on facilities with significant truck volumes by not providing for guidance for heavy vehicle percentages greater than 25%. The objective of this research is to quantify the impact of heavy vehicles on multilane highway and/or freeways for heavy vehicle percentages of greater than 25%.
    Project Amount
    $ 60,142
    Modal Orientation
  • Highways
  • Technology Transfer Activities
    The most common reference for analyzing the operational characteristics of multilane highways and freeways is the Highway Capacity Manual (HCM). The general procedure used by the 2000 HCM to account for heavy vehicles is to use a heavy vehicle adjustment factor that converts heavy vehicles to passenger-car equivalents. In the 2000 HCM, this heavy vehicle adjustment factor, fHV, is independent of the percentage of heavy vehicles for extended highway and freeway segments. It varies by percent of heavy vehicles for specific grades but the tables in the 2000 HCM only provide analysis guidance for heavy vehicle percentages of 25% or less. Nebraska's highways carry a significant portion of heavy vehicle (trucks, buses and RVs) traffic. The NDOR 2004 Statewide Traffic Flow Map indicates that on I-80 alone, the percentage of AADT represented by heavy commercial vehicles is more than 25% from Lincoln to the Wyoming border. Just west of the I-80/I-76 junction on I-80, this percentage reaches a maximum of 60.9%. The objective of this research is to quantify the impact of heavy vehicles on multilane highway and/or freeways for heavy vehicle percentages of greater than 25%.