Synthesis of Information Related to Highway Practices. Topic 55-20. Traffic Capacity Level of Service Adaptations and Usage

The Level of Service (LOS) concept has been used for over 50 years by state departments of transportation (DOTs) for policy setting, planning, analysis, and communication efforts. Individual adoption of the LOS framework by state DOTs has generally been consistent with AASHTO's Highway Capacity Manual (HCM). However, some agencies have tailored their respective LOS definitions and applications for local conditions and values (such as adjustment of HCM's hard-edged LOS category definitions). Additionally, there are differences in how state DOTs use big data and modern communication tools in their LOS analyses. The objective of this synthesis is to document the practices of state DOTs use of the HCM framework for traffic capacity and LOS analyses. Information to be gathered includes (but is not limited to): (1) State DOT use of LOS as a policy, planning, and analysis tool (as a target or a standard); (2) How DOTs determine LOS relative to traffic conditions (peak commute hour, annual average daily traffic, etc.) and road conditions (harder boundary edge or softer shoulder); (3) Frequency and process of reviewing and updating LOS definitions and applications; and (4) Extent to which big data, modern technology, and visual tools have been used for LOS analyses and public communications.


  • English


  • Status: Proposed
  • Funding: $55000
  • Contract Numbers:

    Project 20-05, Topic 55-20

  • Sponsor Organizations:

    National Cooperative Highway Research Program (NCHRP) Synthesis

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC    20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Nasri, Arefeh

  • Start Date: 20230807
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01884753
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-05, Topic 55-20
  • Files: TRB, RIP
  • Created Date: Jun 9 2023 12:43PM