Lesson

Develop a user-oriented system for displaying travel time messages on dynamic messages signs.

Four American Cities' experiences with Travel Time Messaging on Dynamic Message Signs.


May, 2005
Chicago,Illinois,United States; Houston,Texas,United States; Nashville,Tennessee,United States; Portland,Oregon,United States


Background (Show)

Lesson Learned

The objective of any travel time messaging system is to provide drivers with the necessary means to make informed travel decisions while in route to their destinations. To plan, deploy, and operate a system that upholds user satisfaction, agencies must not overlook certain steps crucial to success. The following lessons are to provide guidance on how to ensure travel time messaging on DMS is meeting the wants and needs of the driving public.
  • Define a target audience to help determine travel time destinations and messaging format. Knowing which drivers will benefit most from travel times displayed on DMS arms agencies with the knowledge necessary to provide travel times to the highest number of interested motorists.
    • Prior to implementing their Advanced Traffic Management System (ATMS) the Oregon Department of Transportation (ODOT) examined four potential target audience groups for travel time messages on DMS.
      1. Local commuter
      2. Local non-commuter
      3. Non-local commuter
      4. Non-local non-commuter
      Due to the fact that the majority of vehicles during weekday hours are local commuters, whose travel is generally more time critical than that of other drivers, ODOT decided that they would be the primary target audience for the travel time system. This information helped ODOT in determining travel time destinations.
  • Accommodate difficulties in accurately estimating travel times by displaying travel time messages in ranges. If drivers find travel times displayed on DMS to be consistently inaccurate they may begin to not trust the information and not use it when making travel choices. In the absence of 100% accurate travel times, it is better to provide drivers with a time frame (e.g. 4-5 minutes) for when they’ll reach their destination, rather than be inaccurate in trying to estimate exact travel times.
    • In Nashville, due to limited coverage of speed sensors in areas further outside the city, the Tennessee Department of Transportation (TDOT) provides estimated travel times in a 2-3 minute range (e.g., 6-9 minutes) thus allowing a + 1-1.5 minute variation in travel time.
    • In Portland, ODOT displays travel time messages in two minute ranges (i.e. 7-9 minutes) during normal traffic conditions and in up to four minute ranges during periods of heavy congestion.
  • Display travel times in a concise, easily comprehendible format. Driving on highways and interstates requires that full attention be paid to the surrounding traffic conditions, especially during times of congestion. Single car drivers have little time to look out their window, read, and dissect information presented to them. To allow motorist to focus on their driving, it is imperative that travel times displayed on DMSs be clear and concise.
    • In the Chicago Metropolitan Area travel times are right justified and provided in one of two formats, depending on the number of destinations displayed.
    • In order to reduce driver distraction, DMS messages in Portland are single phase only.
    • Survey results in Houston indicated that drivers prefer single phase messaging, which has become the preferred format for TranStar. Only when highly important information needs to be displayed are double phase messages used.
  • Deploy DMS prior to key decision points where commuters can decide to take alternate routes. Providing travel times well in advance of decision points allows drivers the ability to make the best route choice and can cut down on the potential for rash decisions, that can lead to accidents. To know exactly where these “key decision points” are located it is important for agency staff to have a firm understanding of commuting patterns in the region where DMS is being deployed.
  • Solicit driver feedback to determine what information is most desired on DMS. DMS are used for displaying various types of information beyond travel times. In most cases there is a hierarchy for what information is to be posted on DMS - incidents, construction, and amber alerts usually taking precedence. However, drivers may have a different opinion on what information should be displayed, so agencies may wish to survey motorists to see what they deem to be the most vital information to their commute. Agencies can use this feedback as a useful tool in developing and/or updating the hierarchy for which information is displayed on DMS.
    • Respondents in a customer satisfaction survey, conducted by the Texas Department of Transportation, stated that while incident information is nice to know, travel time information is also needed to determine how the incident affects their travel.
    • Through customer e-mails and calls, the Illinois State Toll Highway Authority (ISHTA) learned that drivers don’t like when information is displayed on DMS in place of travel times. It has been noted that when a non-incident related message is posted during a time at which travel time information is normally posted, ISTHA receives negative feedback from drivers.
The level of driver satisfaction in travel time messaging on DMS will vary from city to city. Based on the experiences of functioning travel time messaging systems in cities across the country, these lessons are to serve as guidance to agencies seeking deployment. As travel time messaging is in place to assist drivers in their decision making process, any system should be planned, deployed, and operated with the driver in mind. To provide travel times that are truly useful, they must be accurate and easily understood. Defining a target audience and soliciting their feedback is another step key to success. By taking these lessons into consideration, agencies can work to gain and/or maintain driver satisfaction in travel time messaging on DMS.


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Source

Travel Time Messaging on Dynamic Message Signs – Chicago, IL; Houston, TX, Nashville, TN, and Portland, OR

Author: Federal Highway Administration Office of Operations

Published By: Federal Highway Administration

Source Date: May, 2005

Other Reference Number: Chicago - FHWA-HOP-05-049; Houston - FHWA-HOP-05-051; Nashville - FHWA-HOP-05-050; Portland - FHWA-HOP-05-048

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Lesson Contacts

Lesson Analyst:

Jane Lappin
Volpe National Transportation Systems Center
617-494-3692
jane.lappin@volpe.dot.gov


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Lesson ID: 2007-00403