Traffic Control Strategies in Work Zones With Edge Drop-Offs

Pavement and shoulder edge drop-offs commonly occur in work zones. The depth of these elevation differentials can vary. The potential hazards associated with pavement edge differentials depend on several factors including depth of the drop-off, shape of the pavement edge, distance from traveled way, vehicle speed, traffic mix, volume, and other factors. This research was undertaken to review current practices in other states for temporary traffic control strategies addressing lane edge differentials and to analyze crash data and resultant litigation related to edge drop-offs. An objective was to identify cost-effective practices that would minimize the potential for and impacts of edge drop crashes in work zones. All of the states surveyed indicated that edge drop-off treatment is initiated before a depth of three inches is encountered. The elevation differential warranting the use of temporary traffic barriers varies from two inches to two feet, depending on individual state policy. No major deficiencies were identified in the current temporary traffic control procedures used by the Iowa Department of Transportation for work zones that include pavement edge differentials. The use of a benefit/cost analysis may provide guidance in selection of an appropriate mitigation and protection of edge drop-off conditions. Development and adoption of guidelines for design of appropriate traffic control for work zones that include edge drop-off exposure, particularly identifying effective use of temporary barrier rail, may be beneficial in Iowa.