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Travel Time Displays Prior to Freeway Entrances

Many transportation agencies now provide real-time travel time information to motorists via changeable message signs (CMS) on freeways. Consistent with previous research, the Transportation Management Center (TMC) Pooled Fund Study (PFS) project "Driver Use of En Route Real-Time Travel Time Information" found that while motorists valued en route real-time travel time information, it was difficult to identify much actual influence of travel time displays on driver route choice and diversion. It appears that once committed to a freeway route, it is difficult to get motorists to divert. Current practice in providing travel time information generally makes use of existing CMS on the freeway. The travel time information is typically provided when higher-priority messages do not over-ride them. The location of the travel time display may not necessarily be optimal for supporting driver decisions and encouraging diversions from planned routes to make better use of system capacity. Travel time displays could have more influence on trip-making if they are provided prior to the driver's point of commitment to a freeway route. Freeway entrances are often key choice points on a commute, where a driver commits to entering a freeway or remaining on a surface street route. Commuters express frustration at the absence of better decision information at this key point. Examples of travel time or congestion displays on arterials in advance of a freeway entrance were found both in the U.S. and in foreign practice, but were not common. Examples include the Traffic Condition Signs used in Melbourne, Australia as part of the VicRoads Drive Time System and an Illinois DOT program in the Chicago area that has now implemented 14 sites. Although current practice on this is limited, existing implementations indicate that it is practical and well-accepted by the public. There is no standard practice for such displays.

Transportation agencies may be collecting and providing real-time information that is helpful to motorist decision making but they currently may not display it where and when it may have its greatest effect on route choices and diversions. A further issue is the extent to which the provision of travel time information for surface street routes, in addition to freeway travel times, can promote effective routing decisions. Travel times for arterial routes are not commonly provided and are more problematic, but may have substantial benefits as data collection technology and data processing capabilities make this more feasible.

The objective of this task order is to compare and quantify motorist response to real-time travel time displays at freeway approaches compared to displays located on the freeway itself. The research will determine the benefits and effectiveness of travel time signs on arterial approaches to freeways and develop recommendations for the design and use of such displays, including information content, format, sign location and warrants. The focus is on freeway travel time information (the current state of practice), but some experimental attention shall also be directed to provision of arterial route travel time estimates.

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Contact Information

To request final documents or materials related to this project, provide feedback and comments, report errors in the final report, or web site questions, contact:

Jimmy Chu