Mitigating Work Zone Safety and Mobility Challenges through Intelligent Transportation Systems: Case Studies
The primary objective of this report was to document several case studies of work zone ITS used to mitigate safety and mobility issues at work zones. Commercial off-the-shelf (COTS) systems were used and tailored designs developed to leverage ITS in work zones. The following lessons were drawn from project information presented in the source document.
Work Zone Traffic Mobility Monitoring in Salt Lake City, Utah.
The purpose of this project was to install Bluetooth technology on the Bangerter Highway (SH-154) in Salt Lake City and examine the potential benefits of a performance-based contracting method used to assure work zone traffic mobility was maintained during the construction of three intersections and one grade separated interchange. Concerned about travel times and construction induced delays, a performance-based contract specification was developed to potentially assign liquidated damages to the construction contractor if traffic conditions degraded below agreed to levels as a result of contractor performance.
The Utah DOT (UDOT) used Bluetooth to monitor work zone traffic conditions and contractor performance. Once calibrated, the Bluetooth system worked as intended, however, UDOT and the contractor had challenges reaching consensus on the exact number of Bluetooth matches required to accurately estimate travel times between specific locations over given time periods. Ultimately, a value of five Bluetooth matches per 15 minute time period was accepted as the minimum.
Results from field testing indicated the warning system enabled UDOT and the contractor to become aware of operational problems much sooner than would have been possible otherwise. Operators used the system in conjunction with existing camera assets to quickly confirm incidents and dispatch response personnel. The system also gave contractors more confidence to request relaxation of lane closure restrictions as needed to accommodate more work. The UDOT identified the following lessons.
- Ensure that traffic monitoring levels match project needs. For this project UDOT and the contractor monitored 48 different movements. However, only a few key movements were of primary interest. Traffic mobility may have been monitored with less data analysis work.
- Allow adequate time to calibrate Bluetooth readers to maximize accuracy and reliability. It took approximately two weeks for UDOT and the contractor to calibrate the system. It was important to identify intersections or locations near businesses where vehicles may sit for extended periods. In these areas it was important to account for device processing time to limit potential for multiple counts of the same vehicle.
- Expect a significant simulation modeling effort to determine performance threshold levels. Agencies may need to monitor conditions continuously during peak and non-peak hours.
- Consider the potential for non-construction related impacts. Agencies will need to differentiate between contractor decisions and behaviors, and other events such as incidents that are unrelated to contractor control.
Overall, UDOT and the contractor agreed that Bluetooth was the best way to monitor delay during this project because the project area had a variety of movements and numerous access points.