In 2003, the Federal Highway Administration (FHWA) began the Work Zone Mobility and Delay Reporting Assessment to document the tangible benefits of using ITS in work zones in a quantitative way. The purpose of the study was to highlight "before and after" analyses that quantify the mobility and safety benefits of using ITS applications for work zone traffic management. The study intended to increase the knowledge and promote further use of deploying ITS solutions for work zone management.
The study analyzed data from five sites:
- District of Columbia
- North Carolina
These sites were selected because the construction project showed significant potential to have a measurable impact on traffic conditions, creating a situation where ITS could be used to reduce the impact.
In 2004, The Michigan Department of Transportation (MDOT) deployed a Dynamic Lane Merge System in the northbound lanes of US-131 in Kalamazoo. The construction area were approximately 11 miles long. Dynamic lane merge systems are deployed to control traffic at merge areas by promoting early or late merging. Early merging smooths flow by creating a no passing zone upstream of the work zone closure. Late merging encourages motorists to use both lanes to minimize queue spillover. The site in Kalamazoo deployed a Dynamic Early Merge System. The objectives of the system deployment were to reduce aggressive driving at the merge point, smooth traffic flow through the merge area and reduce delay from aggressive passing at the merge area. The Dynamic Lane Merge System components included traffic sensors, trailers with solar powered flashers, equipment, and batteries, dynamic message signs, and communication devices.
In this case, system deployment and construction began at the same time, so there was not an opportunity to establish baseline conditions. The intention was for the analysis to be prepared for the "without ITS" condition using data from the southbound approach while the "with ITS" condition was prepared using data from the northbound approach since the system was deployed northbound only and construction was performed in both directions. However, once construction started, there were no congestion issues in the southbound direction, so the analysis was performed comparing data in the northbound direction during time periods when the system was activated (flashing) with time periods when the system was not activated (trailers not flashing). Data were collected for a two week period from September 20 to October 1, 2004. Data collection included observations, crash data, travel time runs, and system data.
The results of the field observations show there was a significant reduction in the number of forced merges and dangerous merges when the system was activated. Queues were present on the days the flashers were "on" indicating that vehicles likely merged in advance to avoid forced or dangerous merging approaching the work zone taper. Results indicated a seven fold reduction in forced merges and a three fold reduction in dangerous merges when the system was activated compared to when the system was not activated. These findings indicate that using ITS solutions to enhance the safety performance of the highway during construction is a valid hypothesis.
These results are also found in the document - Benefits of Using Intelligent Transportation Systems in Work Zones: A Summary Report, Federal Highway Administration, April 2008. http://ops.fhwa.dot.gov/wz/its/wz_its_benefits_summ/index.htm
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