Under NCHRP Project 3-69, 'Design of Construction Work Zones on High-Speed Highways', researchers at the Pennsylvania State University developed guidance for the design of geometric features, including horizontal and vertical alignment, cross-sectional features, and temporary concrete barrier placement. The research team also developed a work zone speed prediction model that estimates free-flow vehicle speeds through two types of construction work zones on four-lane freeways: single-lane closure and median crossovers. The research team reviewed the literature and ongoing research related to work zone design and safety. A survey of state DOTs was also conducted. Survey responses and a review of state DOT websites provided substantial information on current DOT work zone design policies and guidelines. The survey also identified priority topics associated with the design of construction work zones, and these priorities guided the research effort. Seventy-five percent of the states responding to the survey ranked improved guidance on traffic barriers and design as the “most important/critical” need. The roadside design and barrier placement guidance includes a discussion of the clear zone concept and its applicability to construction work zones, the identification of work zone hazards that may require treatment or shielding, and the use of benefit-cost analysis for roadside safety treatment decisions. The subject of speed is inextricably connected to work zones. There is a widely held perception that speed is one of the most significant factors in road crashes. The work zone speed prediction model enables designers to develop a speed profile to detect inconsistencies in construction work zone designs. (Author/publisher) This report may be accessed by Internet users at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_581.pdf
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