Knowledge Resources

During an extensive bridge and highway reconstruction project on Interstate 55, the Illinois Department of Transportation (IDOT) implemented a Real Time Traffic Control System (RTTCS) to ensure safety and mobility during construction. The system successfully monitored traffic along the busy interstate between Springfield (the state capital) and St. Louis, the location of a busy airport serving southern Illinois and eastern Missouri. IDOT reported that the system performed well, with little downtime. In addition, IDOT staff stated that they would utilize this type of system again in a similar project. The IDOT shares the following experiences with other implementers that may choose to utilize ITS in a work zone.

• Involve agencies responsible for 911 and other emergency response operations during system planning and design. This effort can help facilitate a coordinated response to incidents during the roadwork.
• Use a proactive approach to building public awareness of the project. Successful techniques include holding press conferences, issuing news releases, and keeping local media up to date.
• Assess when it is appropriate to use a work zone ITS application and what type of system best meets the site-specific needs.
• Ensure that software/systems engineers and transportation engineers use common terminology during the requirements definition process.
• Include the vendor's engineering staff, in addition to vendor marketing staff, in early discussions of vendor capabilities.
• Allow significant time for system calibration during initial implementation of queue-length detection systems. The calibration process will likely take longer than the best estimate of the time required. The implementation of this system required system calibration that was complicated by the absence of significant traffic congestion. Consequently, the initial deployment phase lasted longer than anticipated.
• Expect the need to recalibrate detection systems during the course of the project. IDOT required that the system be deployed on I-55 and tested two weeks prior to initiation of reconstruction activities. The only difficulty encountered was that there was no significant congestion prior to the start of the reconstruction project, which prevented complete calibration of the traffic detection system. Consequently, recalibration of the system was required after the work zone was in place.

IDOT staff identified several benefit areas for the RTTCS system used in this project. The staff reported benefits in both mobility and safety. Despite the work zone location on a busy interstate, the IDOT staff reported no significant traffic backups while the RTTCS system was in place. For the duration of the construction project, only two crashes occurred which were attributed to other causes than the work zone. In addition, there was a significant downtrend in traffic violations after DMSs started notifying drivers approaching the work zone of the number of citations issued in the work zone. This lesson suggests that using ITS in work zones, such as the RTTCS, can be very successful in ensuring safety and mobility within the work zone.