Work Zone Mobility and Safety Program
Photo collage: temporary lane closure, road marking installation, cone with mounted warning light, and drum separated work zones.
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Caltrans I-15 Devore Case Study

The California Department of Transportation (Caltrans) successfully completed a rapid-rehab work zone project in Devore, California in 2007. This project involved completely rebuilding truck lanes in both directions on a 2.8 mile portion of Interstate 15 (I-15). Caltrans estimated that this work would take 10 months using traditional nighttime closures. However through careful planning, impacts analysis, and public outreach before and during the project, Caltrans was able to complete the work in two 9-day periods using continuous closures with 24/7 operations, resulting in minimal impact to travelers and the surrounding community. Much of what Caltrans did to make this project a success provides an example of the type of practices that should come about more as a result of the Work Zone Safety and Mobility Rule.

Impacts Assessment

Caltrans took a comprehensive approach to examining all of the potential effects of implementing a road closure in an area that is known for high traffic volumes both on weekdays and weekends. A number of traffic analysis approaches, including Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) and the Highway Capacity Manual, were used to evaluate four proposed road closure scenarios:

  • Two 9-day continuous closures, one roadbed at a time (total duration of 400 hours).
  • Eight 72-hour weekday closures (total duration of 512 hours).
  • Fourteen 55-hour weekend closures (total duration of 770 hours).
  • 220 10-hour nighttime closures (total duration of 2200 hours).

The analysis found that the one-roadbed continuous closure (24 hours a day, 7 days a week) was the most economical scenario. This type of closure would require 80% less closure time, 29% less road user cost due to traffic delay, and 28% less agency costs for construction and traffic control than the series of 10-hour nighttime closures. However, Caltrans initially decided to use the 72-hour weekday closure approach, the second most economical alternative, due to concerns about maximum possible delays. They were concerned that the potential for 120 minutes of maximum peak-hour delay on weekends, which could occur with the one-roadbed continuous closure or 55-hour weekend approaches, would be more of a burden on travelers than the projected 75 minute maximum delay on weekdays.

Caltrans held public meetings approximately one month before the scheduled closures to discuss the planned approach with local residents and listen to their concerns. Caltrans also placed a survey on the project web site to gather comments and concerns. Discussions at the public meetings and the survey responses indicated that the public was not happy with the proposed approach, fearing congestion and delays over the extended period of 512 hours that the series of 72-hour weekday closures would take. Respondents also felt that Caltrans was favoring weekend travelers going to Las Vegas by closing the road during the week but not the weekend. As a result of hearing the public's concerns about the impacts, Caltrans decided to implement a one roadbed continuous closure scheme with 24/7 operations by combining weekday and weekend closures into one extended period. Using CA4PRS, Caltrans estimated the peak hour delay under the one roadbed continuous closure to be 90 minutes.

Public Outreach and Transportation Operations Strategies

Caltrans promised residents that they would reduce delay during the extended closures by implementing innovative technologies in the construction area. They also committed to a proactive public outreach campaign that would keep residents informed about the project. Caltrans allocated $160,000 (approximately 1% of total project cost) for public outreach materials (brochures, fact sheets, etc.), which is significantly greater than typical outreach programs for Caltrans highway projects. Caltrans also called on stakeholders from around the area, including media personnel, law enforcement, and traffic planners, to work together on this multi-disciplinary project and minimize impacts.

To expedite construction and minimize impacts from the work zone, Caltrans implemented numerous traffic operations and public outreach technologies and strategies as part of its transportation management plan (TMP), including:

  • A project command center equipped with closed circuit television for team coordination and monitoring of construction progress and traffic impact.
  • Contract incentives/disincentives designed to motivate the contractor to complete closures on time or ahead of schedule.
  • A project web site for disseminating project updates and surveying public perception.
  • An automated work zone information system (AWIS) to update travelers with real-time travel information.
  • Creation of one additional travel lane by using the rehabilitated shoulder to carry traffic.
  • A quick change moveable barrier (QMB) system for dynamic lane configuration to maximize lane capacity and minimize traffic disruption. Twice daily (morning and evening), specialized equipment was used to shift the QMB over a lane to allow one extra lane in the peak traffic direction to accommodate rush hour traffic.
  • Safety and community support services, including freeway service patrol, an enhanced work zone enforcement program, and commuter bus service, to help ensure efficient commuter passage through the project area.
  • A multifaceted outreach program to gain public support and measure change in public perception.
  • Mix design of rapid strength concrete to enable the project to be opened to traffic 12 hours after mixing/placement.

Performance Measurement

Caltrans conducted a traffic monitoring study in parallel with the AWIS implementation to quantitatively evaluate the impact of the extended closures on highway network traffic. Traffic volumes and speeds were measured before and during construction. The overall impact of the closures on traffic was found to be acceptable according to the traffic monitoring study. This was further confirmed by web-based surveys also conducted before and during construction. The study found that there was a 20 percent reduction in traffic demand during the closures, which was 10 percent greater than originally planned. This reduction in demand was attributed to Caltrans' extensive public outreach initiatives and traffic management strategies.


As a result of Caltrans' impacts assessment efforts before and during the project, involvement of the public and multiple stakeholders throughout the duration of the project, and use of innovative technologies to manage demand and provide traveler information, the I-15 Devore project was considered a success. The estimated peak hour delay was decreased by 50% from the CA4PRS estimated 90 minutes. At the beginning of the project, 56% of the public surveyed were opposed to the road closures. By the end of the project, 70% of the public surveyed were pleased with the project and the rapid-rehab construction principles used.

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