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.
Managing Traffic During Construction: The Utah DOT I-15 CORE Project Experience
This report highlighted the use of work zone ITS during the I-15 Corridor Expansion (I-15 CORE) project along a 24-mile section of I-15 in the Orem-Provo region of Utah. The project included the addition of two lanes in each direction of travel, and the widening and reconstruction of 10 interchanges and 63 bridges. Initiated in January 2010 the project had a planned duration of 35 months.
Prior to selecting a construction contractor Utah DOT (UDOT) conducted traffic studies to identify alternate solutions for traffic management during the project. The deployment strategy involved improving surveillance and detection on the corridor by adding in-pavement magnetic puck sensors to select freeway segments to enhance ITS assets previously integrated into the fiber optic backbone. Previously installed assets included CCTV cameras, portable dynamic message signs, 511 system, coordinated traffic signals, ramp meters, traffic speed and volume sensors, pavement sensors, and weather sensors. The enhanced network also included real-time travel time displays on static signs to help travelers estimate travel times to nearby cities and decide if they should take an alternate route to avoid work zone congestion.
UDOT was also able to use the system during special events (i.e., football games and fireworks). In these cases, special timing plans were developed for nearby arterials, and information about alternate routes and parking access points were disseminated via portable DMS and the media.
Although the vehicle detection technology used to track vehicles could only detect about one percent of vehicles, and real-time travel time estimates were not accurate at times, UDOT indicated that the system was able to effectively divert traffic from I-15 and accommodate traffic on arterial alternate routes. In some cases UDOT operators had to manually adjust the posted travel times to encourage or discourage diversion. Diversion rates ranged from 20 to 50 percent. Although the effectiveness of the arterial travel time information was limited, UDOT indicated the feature was worthwhile.
UDOT management offered the following guidance.
- Include maintenance of ITS devices in the list of conditions warranting liquidated damages – Although UDOT retained responsibility for operating the ITS deployment during construction, the project design team was responsible for keeping the various ITS devices in the corridor operational. Initially, the contractor was not always timely with making whatever repairs and adjustments were needed to keep the devices working, to the point that UDOT decided to withhold payment on the project until repairs were made. Adding ITS device maintenance as an item with liquidated damages for non-performance could help ensure that the contractor understands the importance the agency is placing on keeping the system operational at all times.
- Leverage the ability of contractors to innovate on how to best accommodate traffic during construction – UDOT was pleasantly surprised with several ideas proposed by the contractor. Using contracting approaches that allow (and reward) contractors for innovative approaches to managing traffic provides benefits to the contractor, agency, and ultimately the traveling public.
- Verify that proposed innovations and technologies will operate as advertised – The arterial street travel time system that the contractor proposed was envisioned to be a good value. However, the technology suffered from a number of issues, ranging from a deployment approach that limited the ability of the system to track vehicles between sensor locations to problems with the sensor devices themselves. UDOT indicated that it would have been preferable to more fully assess the viability of the proposed installation before it was deployed.