Traveler Information and Travel Time Reliability

A number of states and metropolitan areas communicate travel time information and related highway system condition data to travelers. Of roughly 100 metropolitan areas responding to a U.S. Department of Transportation survey conducted in 2006, 27 indicated they displayed travel time information on variable message signs. Besides variable message signs, other communications channels and technology platforms are used to communicate travel time information. These include broadcast media, satellite radio, the Internet, cell phone networks (e.g. 511 and other services for wireless devices), highway advisory radio, and telematics services such as General Motors’ OnStar. Other information besides travel time that may be communicated includes travel speed, congestion, incident locations, alternative routes, work zone locations, and weather. In addition, a number of private sector companies also communicate travel time and related information to travelers through a variety of channels and on different technology platforms. There is strong evidence based on empirical studies that road users are nearly as (if not more) concerned about travel time reliability as about average travel time. Individuals are concerned about being late for work and about missing other important appointments. Motor carriers may be faced with penalties for not meeting service agreements and delivering shipments late. Information about travel time reliability (as opposed to simple information on travel times) is much less frequently communicated to travelers at present. Only a few states and metropolitan areas provide such information for either pre-trip planning or for en route decision making by travelers. An example is Washington State DOT’s 95 percent reliable travel time calculator for highways in the Puget Sound region, which travelers can access over the Internet for pre-trip planning. Travelers do get considerable information about reliability from their own daily experiences. However, there is an overall lack of knowledge about what reliability information is useful to travelers, how best to communicate it to them, how reliability information impacts traveler choices and demand at given times on particular facilities, and how communicating information about reliability affects system performance, particularly in terms of nonrecurring highway congestion. It is recognized that travelers use multiple communications channels at different stages of their journey and also use them to gain additional intelligence about the transportation network and how conditions might affect their journey. Part of the problem with communicating travel reliability information within the transportation network and to travelers is the lack of a shared language about reliability—a lexicon. There are many definitions of travel reliability and some are simply beyond the comprehension of travelers and most professionals. “Reliability” itself is a term of art that may have little meaning to the traveling public. On the other hand, some commonly used concepts such as “buffer time” seem to be intuitively understood by many. Travelers quickly learn to reserve additional time for some journeys on some routes in order to work around nonrecurring delays associated with things like incidents, bad weather, work zones, special events, and malfunctioning traffic control devices. A key issue in this research is to find the right combinations of words, numbers, symbols, layout, lighting, color, and spacing to communicate information about travel time and reliability to travelers using a particular communications channel and technology platform. Another key issue is to find the best combination and arrangement of information so that travelers may make optimal travel choices from their point of view. Important choices include whether to take a trip or not, departure time, mode choice, and route choice. Information about travel time reliability is important for free roads but also for priced roads, which are likely to become more prevalent. This project will be inherently more valuable in urban areas where nonrecurring congestion is most severe and widespread. Approximately half of all traffic congestion in urban areas is nonrecurring. This project will focus on urban areas, however, many of the research results could be transferable to rural areas that experience travel unreliability due to weather, incidents, and other sources of nonrecurring congestion. Almost all congestion in rural areas is nonrecurring in nature. This project has multiple objectives, which are to: (1) Better understand the current and near-term future dimensions of the travel time/travel reliability information marketplace, including technologies, the roles of the public and private sectors, and choices (both free and priced) available to travelers. (2) Better understand what network travel time and travel reliability information travelers require, particularly in complex metropolitan environments where many travel choices are possible. Better understand how travelers would use improved information. (3) Determine how best to communicate travel time reliability information to travelers so that they can understand it and use it to make optimal travel choices. The focus is on content and format of travel time reliability information appropriate to specific technology platforms and communication channels. Develop a guide to help providers of traveler information ensure that information regarding travel time reliability is offered in a manner that is most useful to travelers. (4) To the extent possible, quantify the potential for improvements in the communication of travel reliability information to affect traveler choices such that positive impacts on system performance occur, e.g. improved transportation system reliability. (5) Develop a simple and standardizable lexicon for communicating travel time reliability concepts among transportation professionals and travelers. (6) Develop prioritized, near-term strategies for improved dissemination of travel time reliability information and provide guidance for state departments of transportation and other public sector transportation agencies that are contemplating providing travel reliability information to travelers.


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  • Status: Completed
  • Funding: $998553.00
  • Contract Numbers:

    Project L14

  • Sponsor Organizations:

    Strategic Highway Research Program 2

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC    20001
  • Project Managers:

    Hedhli, Abdelmename

    Murthy, Gummada

  • Performing Organizations:

    Texas A&M University, College Station

    Department of Mechanical Engineering
    College Station, TX  United States  77843-3123
  • Principal Investigators:

    Kuhn, Beverly

  • Start Date: 20090901
  • Expected Completion Date: 0
  • Actual Completion Date: 20130331
  • Source Data: RiP Project 15545

Subject/Index Terms

Filing Info

  • Accession Number: 01464740
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project L14
  • Files: TRB, RiP
  • Created Date: Jan 3 2013 2:48PM