Corkle, Jacqueline

This report describes the results of studies on the use and effectiveness of rumble strips, including a survey of Minnesota county engineers and a simulation conducted at the University of Minnesota Human Factors Laboratory. Sixty-eight of 87 counties responded to the survey. Of the 68 respondents, 56 install in-lane rumble strips. The survey also asked respondents to describe the guidelines that they used to designate areas for rumble strip installation. As part of the simulation study, test subjects drove in a simulator through a designed experiment to measure the effectiveness of in-lane rumble strips. The results of this study showed different braking patterns between intersections with in-lane rumble strips and those without rumble strips. Those with rumble strips braked earlier and harder. The report recommends that shoulder rumble strips be used in areas with high rates of run-off road crashes. Before-and-after studies have shown conclusively that shoulder rumble strips have reduced run-off road crashes by 20% to 72%. It also recommends a follow-up study on in-lane rumble strips involving drivers that are sleep deprived, under the influence of alcohol, or driving in poor conditions.

This report highlights the findings of a project to determine the impact of traffic calming strategies on driver behavior, traffic flow, and speed. Researchers used a number of different approaches, including a literature search to determine results at a national level and local before-and-after studies in areas that implemented new traffic calming strategies. Researchers also compared an actual street before and after implementation of traffic calming devices to a driver simulation study of a street with and without traffic calming devices. Research results indicate that traffic calming can have a limited impact on average driver speed. The greatest impacts on speed often occur in reducing the number and speed of outliers, or those who travel at speeds greater than the 85th percentile speed. The report details the impact of different types of traffic calming strategies on traffic speed and volume.