Findings

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	$73,806.64	$2,327,215.90
	Worst Case	$73,022.29	$2,284,247.04
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	-	3.02
	Worst Case	-	3.08
20 Year Cost	Best Case	$96,193.60	$2,537,592.12
	Worst Case	$95,642.90
20 Year Benefit	Best Case	4 fatalities prevented	5 fatalities prevented
	Worst Case	3 fatalities prevented
20 Year Incremental Benefit:Cost Ratio	Best Case	-	2.79
	Worst Case	-	5.57

Table 10.2 Comparison of Alternatives for Curves