Variable Advisory Speed Systems (VASS) provide drivers with advanced warning regarding traffic speeds downstream to help them make better decisions. Vehicle use on highways is increasing and the need to improve highways brings increased construction of highways, which increases the need for reducing the number of traffic lanes thus reducing capacity during construction. This often causes queues at the entrance to work zones. The purpose of this study was to evaluate the effectiveness of a VASS at mitigating queues in work zone entrances.

This report summarizes and evaluates the important findings from the literature review of the studies on work zone speed control techniques. The following treatments are included in this report: 1) flagging, 2) lane width reduction, 3) law enforcement, 4) changeable message signs (CMS), 5) rumble strips, and 6) flashing beacons. The effects of the speed control treatments on speed and traffic flow are evaluated based on: A) experiences with treatment, B) effects of treatment on speed, C) effectiveness of treatment, and D) comments about treatment. A brief description of the conditions under which the treatments were applied is provided, and the speed reduction effects of each technique are discussed. A reference matrix was prepared to identify publications related to each type of speed reduction treatment used in work zones.

The Iowa Department of Transportation (DOT) has made improving work zone (WZ) safety a high priority. Managing vehicle speeds through work zones is perceived to be an important factor in achieving this goal. A number of speed reduction techniques are currently used by transportation agencies throughout the country to control speeds and reduce speed variation at work zones. The purpose of this project is to study these and other applicable work zone speed reduction strategies. Furthermore, this research explores transportation agencies' policies regarding managing speeds in long-term, short-term, and moving work zones. This report consists of three chapters. The first chapter, a literature review, examines the current speed reduction practices at work zones and provides a review of the relevant literature. The speed control strategies reviewed in this chapter range from posting regulatory and advisory speed limit signs to using the latest radar technologies to reduce speeds at work zones. The second chapter includes a short write-up for each identified speed control technique. The write-up includes a description, the results of any field tests, the benefits and the costs of the technology or technique. To learn more about other state policies regarding work zone speed reduction and management, the Center for Transportation Research and Education conducted a survey. The survey consists of six multipart questions. The third chapter provides summaries of the response to each question.