About the research
The Iowa Department of Transportation has made improving work zone safety a high priority. Managing vehicle speeds through work zones is perceived to be an important factor in achieving this goal. The purpose of this project was to study applicable work zone speed reduction strategies.
The literature review chapter concluded that flagging and police enforcement speed reduction strategies have had very positive impacts in reducing work zone speeds. They are, however, labor intensive and can become costly with long-term use. Replacing these strategies with innovative technologies, such as robotic flaggers and photo-radar enforcement machines, may be practical, more cost-effective solutions. The most effective speed reductions will probably involve some combination of techniques.
To learn more about other states’ policies regarding work zone speed reduction and management, surveys were sent to other state transportation agencies. During construction activities, most participating state agencies reported reducing speed limits to 10 mph below the normal posted speed. Among the 12 identified speed reduction strategies, the use of regulatory speed limit signs and police enforcement are the most common practices reported by the agencies. However, only 7% of the participating agencies consider the use of regulatory signs to be an effective speed reduction strategy. This may be compared with 70% of agencies that consider engaging police enforcement to be very effective at imposing speed limit compliance in work zones. The survey further indicates that the use of changeable message signs by 18 out of 34 agencies might be an indication of their potential in reducing work zone speeds.