A Benefit Cost analysis shows that dynamic curve speed warning signs have 30 percent effectiveness and an incremental B/C ratio between 2.79 to 5.57 for curves that already have static curve warnings.

December 2009

Summary Information

In this study, new emerging technologies were studied against traditional infrastructure-based safety systems for reducing road departure crashes on both tangent segments and curves in Minnesota. These emerging technologies and traditional infrastructure solutions were evaluated based on their effectiveness in reducing crashes, market penetration, legal implications, cost effectiveness and their contribution to the "To Zero Deaths" initiative (TZD). An optimum solution has been provided. The benefit-cost analysis was conducted based on results of a before and after study, as well as a cross-sectional study, conducted on a sample of road segments and curves in Minnesota.


Minnesota DOT (Mn/DOT) already had some form of static warning sign for 80 percent of curves on their trunk highways, so they investigated the incremental benefit of adding Dynamic Curve Speed Warning signs that use radar for speed detection. These signs have a high efficiency value of 30 percent and would be used on curves where there have been more than 10 crashes in two years.

Mn/DOT had already implemented most static, infrastructure-based solutions on its most dangerous curves, so an incremental benefit-cost analysis (BCA)was conducted in order to determine the additional benefits that could be gained from utilizing dynamic curve speed warning systems on top of previous solutions such as static signage or rumble strips. The BCA was calculated for both 10 and 20 year horizons and assumes that the dynamic signs would be added to all curves that currently have static curve warning signs. Calculations for the computed benefit-cost ratios can be found in Appendix K of the source document.

Curve Speed Warning Sign (Baseline)
Dynamic Curve Speed Warning Sign
10 Year Cost
Best Case
Worst Case
10 Year Benefit
Best Case
2 fatalities prevented
3 fatalities prevented
Worst Case
1 fatality prevented
2 fatalities prevented
10 Year Incremental Benefit:Cost Ratio
Best Case
Worst Case
20 Year Cost
Best Case
Worst Case
20 Year Benefit
Best Case
4 fatalities prevented
5 fatalities prevented
Worst Case
3 fatalities prevented
20 Year Incremental Benefit:Cost Ratio
Best Case
Worst Case
Table 10.2 Comparison of Alternatives for Curves

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Benefit:Cost Analysis of In-Vehicle Technologies and Infrastructure Modifications as a Means to Prevent Crashes Along Curves and Shoulders

Author: Jaswandi Tushar Pitale, Craig Shankwitz, Howard Preston and Michael Barry

Published By: Minnesota DOT

Prepared by the University of Minnesota for the Minnesota DOT

Source Date: December 2009



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Benefit ID: 2011-00728