Accessibility Measures in Practice: Guidance for Transportation Agencies

Accessibility is the ease with which travelers can reach valued destinations. Measures of accessibility provide important information to transportation agencies to improve the performance of the transportation system across all modes to better meet human needs. Sometimes the term “accessibility” is used in reference to the specific requirements under the Americans with Disability Act; however, transportation agencies frequently consider accessibility to be a broader concept that is applicable to all user groups and modes and that accounts for distance, travel time, and other costs of reaching valued destinations.  There is a vast research literature describing data, methods, and tools to measure accessibility. Applied tools—proprietary and public—range from large software packages to local implementations by city staff or academic researchers. Data sources include commercial data products, university-led national data processing projects, outputs from metropolitan planning organization (MPO) efforts, and comparative metropolitan analyses from advocacy groups for non-motorized transportation. In current practice at transportation agencies, accessibility measures take many forms and are used as a consideration in planning, prioritization, programming, and project design. For example, a measure focused on the number of jobs that can be reached within a 30-minute commute can be used to evaluate a long-range transportation plan. Comparing projects by how they are anticipated to change the numbers of  reachable jobs can be used to prioritize projects in a statewide transportation improvement program (STIP) or metropolitan transportation improvement program (TIP). A measure can focus on accessibility for subgroups, such as changes to a bus network to increase access to healthcare services for elderly populations. One motivation for using an accessibility measure is that it can provide a user-centric approach to compare tradeoffs between proposed investments, including across modes. Additionally, accessibility measures can be used to understand the distribution of user benefits and costs of specific transportation investments or to more closely link transportation decisions with land use development. Accessibility measures can also serve as performance measures to expand the goal areas included in performance-based planning and programming (PBPP) efforts beyond the federally required transportation performance measures. The specific choice of an accessibility measure is driven by not only available data, but also by the decision-making context. The decision-making context includes the transportation mode available or planned, populations of interest, geographic scale, and other factors, as well as the agency decision point that the selected measure is intended to inform (e.g., system or corridor planning, programming, or project design). As transportation agencies increasingly adopt data-driven and strategic approaches to decision making, the need for measures that can inform those decisions is also increasing. Yet identifying and implementing meaningful accessibility measures can be challenging. To date, there is no standard practice for the selection and use of accessibility measures from among the wide array of accessibility metrics, methods, and tools. Research is needed to characterize and evaluate existing accessibility measures and identify valid and feasible measures for a range of decision-making contexts.  To improve current and future practice, research must be coupled with guidance and support for implementation. The objective of this research is to develop a practitioner-ready resource for transportation agencies on how to select and apply accessibility measures for different decision-making contexts. The resource will include guidance for immediate and mid-term actionable steps for transportation agencies to implement accessibility measures. The project will also include engagement with state departments of transportation (DOTs) and their partner agencies in implementation of accessibility measures. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must represent the proposers’ current thinking described in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach in meeting the research objective. The work proposed must be divided into tasks and or phases. Proposers must describe the work proposed in each phase and task in detail. The research plan should build in appropriate checkpoints with the NCHRP project panel, including, at a minimum, (1) a kick-off web meeting to be held within 1 month of the contract’s execution date, (2) at least one face-to-face interim meeting focused on the review and NCHRP approval of a major interim deliverable, and (3) electronic reviews of other interim deliverables.  The final deliverables will include a resource on accessibility measures for transportation agencies, organized to support agencies seeking measures for particular decision-making contexts. The resource should include: (1) Identifying and describing decision-making contexts for which accessibility measures are appropriate (2) A range of accessibility measures, including simple and complex approaches     (3) Classification of available accessibility measures with information on usability, limitations, and staff and other resources required for each measure (4) Guidance for selecting measures appropriate for the decision-making context and resources available (5) Protocol for determining the parameters for the selected measure (for example, how to select a buffer, destinations included, distance weighting) (6) Case study examples of successful use of accessibility measures. To accelerate the use of accessibility measures, the project will include activities that engage at least three state DOTs and their partners (e.g., MPOs and local governments). Potential activities may include virtual or face-to-face peer exchanges, workshops, technical assistance, hands-on tutorial sessions, or pilot use of the guidance. A memo on implementation will accompany the final deliverables. The implementation memo will outline opportunities for and challenges to wider use of accessibility measures, along with prioritized improvements to current practice in the use of these measures. The implementation memo will draw from the engagement activities of the project to describe productive approaches, anticipated challenges, and resources needed to support state DOT use.


  • English


  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 08-121

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  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:

    Hartell, Ann

  • Start Date: 20190305
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01672246
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 08-121
  • Files: TRB, RiP
  • Created Date: Jun 18 2018 3:02PM