Best Practices in the Use of Hybrid Static-Dynamic Signs
The Florida Department of Transportation (FDOT) has deployed overhead dynamic message signs (DMS) on freeways throughout the state. These DMS are used to quickly communicate important, up-to-date messages to drivers in real-time. Priorities for displaying messages on these DMS are usually given to those related to traffic incidents, construction notices and warnings, route diversion, amber/silver alerts, and special events. When such messages are not on display, the practice has been to display travel times and distances to specific freeway locations, usually an interchange.
While travel times are considered a low-priority for display on overhead DMS, they are nonetheless important information for drivers. Currently, travel times are not displayed when a message with a higher priority, such as for an amber alert and a warning about a future road closure, is in effect. While the SunGuide software does not currently provide accurate travel times under incident conditions, there have been efforts to develop algorithms that will predict incident durations, thus making travel times available during these conditions. However, such travel times will not and cannot be displayed as the DMS would be used to display other related messages. This will create a situation in which travel times are not available when they are most needed, but are available only when traffic is free flowing and travel times are very much predictable. Furthermore, it is also believed that reading messages on these traditional DMS may take longer than reading from static signs, thus creating safety concerns.
An alternative to displaying travel times on traditional DMS is to have them displayed on "hybrid static-dynamic signs," which embed relatively small DMS in static signs. It is believed that these signs provide better legibility and require less time to read. A common use of hybrid signs in the U.S. has been for speed limit signs at temporary work zones. Hybrid signs, however, have increasingly been used in other applications, such as for managed lanes, where such signs are used to display dynamic messages including toll rates, travel times, and lane closure. Because these signs are smaller and less costly to display and maintain, they may also be suitable for use on major local streets.
The goal of this project is to potentially advance the use of hybrid static-dynamic signs for travel time display and other information. The specific objectives include the following:
- Review existing practices in the use of hybrid signs and the companies that manufacture and market them.
- Identify potential applications of hybrid signs, potential locations in District 4 where such applications may be deployed, and the required infrastructures to support their implementation.
- Design specific MUTCD-compliant hybrid signs for these applications.
- Evaluate the effectiveness of the hybrid sign designs, including their potential benefits over traditional DMS, for different driver groups.
- Conduct a stated preference survey of road users to assess the preference for and the usefulness of potential hybrid sign applications.
- Produce standard application documents for new hybrid sign designs to submit to FHWA for review and approval.