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This research explores the potential safety effects of dynamic signing at rural horizontal curves. It accomplishes this by asking two key questions. First, is there a relationship between a vehicle's speed on the approach to a curve and the ability to successfully navigate the curve? Second, is there a difference between static and dynamic signing in the ability to reduce the speed of high-speed vehicles? Researchers assembled an off-the-shelf hardware and software package and deployed it at a four-degree curve along CSAH 54 in rural Dakota County. If purchased new, the package would cost about $50,000; however, an agency could deploy the components necessary to perform dynamic curve warning (a changeable message sign and radar unit) for approximately $10,000. The field test collected vehicle speed data for about 2,600 vehicles. In addition, researchers tracked and videotaped 600 vehicles. The data suggest, and statistical tests confirm, that the initial speed of a vehicle before entering a curve does have a statistically significant effect on the probability of successfully navigating through the curve. The data also indicated that the overall effect of the dynamic curve warning system on vehicle speeds is relatively small. However, the dynamic system had a much greater effect on high-speed vehicles than the static curve warning sign and the dynamic system significantly improved the ability of the high-speed vehicles to successfully navigate through the curve.

This study presents statistically reliable conclusions based on a comparison of the operational and safety characteristics of rural intersections without turning lanes, with bypass lanes, and with left turn lanes. The basic work tasks associated with the research study included: a literature search of nationally published research reports, a survey of bypass lane use, a summary of the legal issues associated with passing on the right, operations and safety analyses, and a review of Minnesota Department of Transportation (Mn/DOT) recommended design guidelines and design features. The results of the safety and operations analyses did not offer a high degree of statistical reliability. However, a comparative crash analysis and a before-versus-after analysis suggested that it is impossible to conclude that the use of a bypass lane provides a greater degree of safety, and, therefore, bypass lanes should not be used as a safety device. There also were some concerns expressed about safety issues at four-legged intersections. Recommendations included: Revise Mn/DOT turn lane policies to at least reduce or eliminate the use of bypass lanes at four-legged intersections; Consider developing a shorter and less costly exclusive left turn lane design; and Offer designers positive guidance regarding the use of left-turn lanes, through a prioritized approach based on the functional classification of the major roadway.

The primary objective of this report is to present statistically reliable conclusions relative to the changes in crash frequencies and other crash characteristics at isolated rural intersections associated with the installation of street lighting. It was found through a comparative analysis of over 3,400 rural intersections and a Before versus After analysis of a sample of 12 intersections that the installation of street lighting reduced both nighttime crash frequencies (25% to 40%) and crash severity (8% to 26%). A Benefit – Cost analysis using statistics from the Before versus After analysis found that crash reduction benefits associated with the installation of street lighting at rural intersections outweigh the costs by a wide margin. As a result of the analysis, it was concluded that the installation of street lighting at rural intersections is a low cost and very effective strategy for mitigating nighttime crashes. This strategy should be added to the traffic engineer’s toolbox and agencies should be encouraged to increase the use of streetlights at rural intersections in order to reduce crashes and improve motorist guidance. It was also concluded based on a comparison to the results for other recent research that the use of street lighting to reduce nighttime crashes at rural intersections would likely be far more effective than either rumble strips or flashing overhead beacons.