The Federal Highway Administration (FHWA) organized a pooled fund study of 26 States to evaluate low-cost safety strategies as part of its strategic highway safety effort. One of the strategies chosen to be evaluated for this study was flashing beacons. Three types of flashing beacons--intersection control beacons, beacons mounted on STOP signs, and actuated beacons--were considered collectively at stop-controlled intersections. This strategy is intended to reduce the frequency of crashes related to driver unawareness of stop control at unsignalized intersections. Geometric, traffic, and crash data were obtained at stop-controlled intersections for 64 sites in North Carolina and 42 sites in South Carolina. Empirical Bayes methods were incorporated in a before-after analysis to determine the safety effectiveness of installing flashing beacons, while accounting for potential selection bias and regression-to-the-mean effects. Overall, installation of flashing beacons in North Carolina resulted in statistically significant reductions in total, angle, and injury plus fatal crashes. The intersections in South Carolina experienced very little change following the introduction of flashing beacons. The combined results from both the States supports the conclusion that an angle crash reduction of a 13 percent and an injury and fatal crash reduction of 10 percent can be expected. The economic analysis based on the combined results for angle and nonangle accidents from both States indicates that standard flashing beacons and some of the actuated ones (i.e., the less expensive beacons) are economically justified, but that a benefit cost ratio of 2:1 may not be achievable for the more expensive actuated beacon types.

The Development of Crash Modification Factors program studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections. Improvements included basic signing and pavement markings. This strategy is intended to reduce the frequency and severity of crashes at stop-controlled intersections by alerting drivers to the presence and type of approaching intersection. Geometric, traffic, and crash data were obtained at three- and four-legged, two- and four-lane major road, and urban and rural stop-controlled intersections in South Carolina. To account for potential selection bias and regression to the mean, an empirical Bayesian before-after analysis was conducted, using reference groups of untreated intersections with similar characteristics to the treated sites. The analysis also controlled for changes in traffic volumes throughout time and time trends in crash counts unrelated to the treatments. The aggregate results indicate reductions for all crash types analyzed (i.e., total, fatal and injury, rear-end, right-angle, and nighttime). The reductions are statistically significant at the 95-percent confidence level for all crash types. For all crash types combined, the crash modification factors (CMFs) are 0.917 for all severities and 0.899 for fatal and injury crashes. The CMFs for rear-end, right-angle, and nighttime crashes are 0.933, 0.941, and 0.853, respectively. The benefit-cost ratio estimated with conservative cost and service life assumptions is 12.4 to 1 for total crashes at unsignalized intersections. The results suggest that the multiple low-cost treatments, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective.

Technical summary of the FHA report FHWA-HRT-17-086 program that studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections.

Evaluation of blank-out signs at intersections where traffic signals are in a flashing mode.