Knowledge Resources

At the start of the iFlorida Model Deployment, FDOT managed about 45 dynamic message signs (DMS) deployed along I-4. Most signs were used to display delay and incident information, with a small number of sign used to display information about local attractions. During the iFlorida deployment and operational period, the number of these signs increased to 60. In addition, 20 variable speed limit (VSL) signs were deployed as part of iFlorida and a number of trailblazer signs were deployed at arterial intersections near the I-4 and I-95 interchange. These signs operated reliably, with about 90 percent of the signs operational, on average. This percentage dropped to 70 percent during the midst of the iFlorida deployment when the Condition Reporting System (CRS) software was experiencing difficulties interfacing with the signs and FDOT resources were focused on correcting other problems with the iFlorida deployment.

A number of lessons learned were identified by observing sign operations during the evaluation with regard to using dynamic message signs (DMS) for traveler information dissemination:

• Validate travel time estimates before being used for traveler information. The CRS software miscalculated travel times that were used for DMS messages, resulting in inaccurate travel times being displayed to the public. One iFlorida stakeholder suggested that the process used to produce travel times for DMS messages should be thoroughly validated before being used in the field.
• In developing software for automating messages posted on DMS, focus on the types of messages that are used often and change frequently. The CRS software included tools to generate travel time DMS messages automatically. FDOT operational policies for these signs meant that congestion messages were used most often during high traffic periods-exactly the time when sign messages changed frequently (because of changes in travel times). This required RTMC operators to manage congestion sign messages manually during rush hour periods while travel time messages, used when congestion was not present, were generated automatically. The workload on RTMC operators might have been reduced if congestion messages were automated rather than travel time messages.
• Include software tools for managing DMS travel time messages manually in the event that the automated travel times become unavailable or unreliable. FDOT experienced significant reliability problems with their travel time network, so that travel time estimates were often unavailable. Although the CRS software was intended to include tools to estimate travel times based on historical values, these tools were not used. When the CRS failed, FDOT discovered that (a) static historical travel times worked well for most of the day and (b) RTMC operators could update signs manually to reflect current travel conditions when congestion occurred, although they made these updates by circumventing the CRS software.

In general, the FDOT roadside signs proved fairly reliable. Prior to the iFlorida deployment, about 90 percent of the forty-four FDOT DMSs were operational. Throughout most of 2005 and 2006, when FDOT was experiencing significant problems with other aspects of the iFlorida deployment, this percentage dropped down to about 70 percent. By early 2007, after FDOT abandoned the use of the CRS to manage sign messages, the reliability of these signs returned to pre-iFlorida levels, even as the number of signs increased from 44 to 60. Reliable messages posted on DMS increase customers’ satisfaction through assisting them manage their en route mobility conditions.