Use recommended practices to provide accurate travel time messages to the public using Dynamic Message Signs (DMS).
Experiences and guidance from the use of DMSs in metropolitan areas.
Atlanta,Georgia,United States; Chicago,Illinois,United States; Cincinnati,Ohio,United States; Columbus,Ohio,United States; Detroit,Michigan,United States; Hampton Roads,Virginia,United States; Houston,Texas,United States; Louisville,Kentucky,United States; Milwaukee,Wisconsin,United States; Nashville,Tennessee,United States; Orlando,Florida,United States; San Antonio,Texas,United States
While travel time messages may be overridden by traffic incident or road construction messages, they can provide valuable motorist information in conjunction with the event messages, as well as after the incident or construction has been cleared if there is residual congestion. Also, special events that typically generate traffic demand that exceeds capacity - fairs, concerts, sporting events - provide additional opportunities for providing travel time information to motorists.
The areas that have been providing travel time messages have found solid public support for the messages. Their experiences have provided a number of recommendations summarized here from the guidance report referenced below.
- Seek feedback from and educate the public before starting to post travel time messages. A campaign of public awareness is critical in order for the time messages to have an initial positive effect. New types of messages often cause motorists to slow down, so any efforts to reduce those "surprise" effects will help motorists more easily adapt to the new messages. Also engaging the public and the media in helping determine destinations and message forms will improve the quality of service and help achieve a positive response to the messages.
- Generate travel times automatically. Travel times should be generated automatically and not require a human operator to manually enter travel time data. All but one of the locations surveyed that provide travel time messages use automated processes to calculate the travel times. They use different technologies to measure the traffic flow, including loop detectors, video detection systems, automatic vehicle identification transponders and toll tags. The traffic data are processed to produce travel time over specified links between identified destinations. It is important to note that effective travel time messages do not require the data to be 100% accurate. Research has indicated that data with error rates of 20% produce useful traveler information. When presenting a range of travel times on DMS the acceptable error rate may be even higher.
- Construct travel time messages to benefit more than the local commuter where there is a mixture of types of travelers. Successful practices from the Atlanta area demonstrate that a relatively simple change to local information can benefit unfamiliar travelers as well. By including the distance to the destination in addition to the travel time, even those travelers unfamiliar with the area can determine the approximate level of congestion ahead.
- Maintain credibility of DMS messages by changing them in a timely manner and by validating the message displayed (1). Displaying messages that are inaccurate leads to motorist confusion and can adversely affect both traffic flow and the transportation agency’s credibility.
Metropolitan Areas Providing Travel Time Messages on Dynamic Message Signs:
- Hampton Roads
- San Antonio
(1) Johnson, Christine M., Policy Memorandum on the Use of Changeable Message Signs, January 19, 2001.
Author: Paniati, Jeffrey and Jeffrey Lindley
Published By: USDOT FHWA
Source Date: 7/16/2004URL: http://ops.fhwa.dot.gov/travelinfo/resources/cms_rept/travtime.htm
Average User Rating
DMS, CMS, VMS, Changeable Message Signs, Variable Message Signs