In 2004, the Federal Highway Administration (FHWA) implemented the Work Zone Safety and Mobility Rule to focus on improving work zone operations. State Departments of Transportation (DOTs) are always looking for tools and applications that can help improve mobility and safety by actively managing traffic through the work zone. ITS applications provide a number of tools that should be considered when looking at options for mitigating traffic impacts that occur during construction. In 2003 an assessment was performed to highlight benefits, lessons learned, and tips from five DOT sites that implemented ITS solutions for work zone traffic 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 applications could be used to reduce the impact. Each DOT developed a list of lessons learned for other DOTs to weigh when considering work zone traffic management.
In 2004, the North Carolina Department of Transportation (NCDOT) designed an ITS work zone solution on a rural section of I-40 west of Winston Salem. The goal of the system was to monitor traffic conditions and improve mobility and safety through the work zone. The work zone was about 4 miles long between the I-40/NC 801 interchange in Davie County and I-40/SR 1101 interchange in Forsyth County and also included a bridge rehabilitation project on I-40 about five miles east of the work zone. The majority of the construction was restricted to night work. NCDOT offers the following lessons when implementing ITS applications as an integral part of the work zone management plan.
- Require communications and technology experts along with traffic engineering experts to design, implement and test ITS deployments for work zone applications. A hardware / software / communications expert representing the agency should be in regular (e.g., daily) contact with a traffic engineer to ensure full system functionality and that the ultimate goals of the system are achieved. For this deployment, NCDOT engineers coordinated with vendor communications experts to deploy the system. Agencies should not rely on the construction contractor of the system vendor to assure the system is operating as intended.
- Discuss in sufficient detail the concept of operations for the system with the vendor to reach an understanding of exactly how it will process information, and determine what messages to post. The vendor needs to understand the goals the agency is trying to accomplish with the work zone deployment. Technology can easily become a “black box” where data are input and actions result. The deploying agency should be familiar with all aspects of system functionality and should guide the vendor, not the other way around.
- Verify techniques to validate the outputs of the system and refine system operating procedures as needed prior to implementation. Agencies should perform a dry run using a test data set to simulate traffic condition information to monitor the system and verify output before full implementation. In this case the ITS deployment was not completed until after construction started, so the agency had little time to test before implementation.
- Develop performance metrics prior to system implementation to establish specific means of monitoring how well the system worked during the deployment. For this deployment, observation and analysis of interim data proved difficult due to the level of effort needed to access and view preliminary data sets. Therefore, NCDOT relied on the vendor to ensure system functionality and accuracy.
- Use message board controls to prevent conflicting messages from being displayed along the same approach to the work zone area. At this study site, message logs showed that motorists observed conflicting messages, including delay warnings followed by free flow condition messages. This functionality should have been part of the system requirements and tested before implementation.
- Have real-time access to archived system data to identify any issues and monitor system functionality. A Web site could easily provide password protected access to the data being used by the system to make decisions. The Web site for this project provided access to real-time data but did not provide access to the data archives. This too should have been part of the system requirements.
These lessons provide insight into what practitioners and other agencies can expect when deploying a similar ITS work zone solution, providing key insights into how to design successful solutions and tie the design to the objectives identified by the agencies for system operation. NCDOT suggests that in order to have a successful ITS work zone implementation the agency needs to maintain ownership of system operations and not rely solely on the vendor or the construction contractor to assure proper system functionality. This means the agency needs to retain their own system experts; whether they be agency personnel or outside professionals. The agency also needs to be sure system functionality meets their intended goals and objectives, and test the system before full deployment. By adhering to these lessons, other practitioners will benefit from the experience of NCDOT, advancing their knowledge of ITS work zone deployments, improving the safety and mobility of travelers through construction zones.