Safety Effects of Fixed Automated Spray Technology Systems

Abstract

Fixed automated spray technology (FAST) has emerged as a solution to provide quick, effective service delivery to high-risk locations prone to icy conditions or with high traffic volumes. The Colorado Department of Transportation has installed and used FAST on bridges since 1998, with 32 units currently installed on bridges around the state. There is some concern regarding the effectiveness of FAST in reducing accidents during winter weather. Previous studies of FAST have considered the changes to crash occurrence following deployment, but these studies were basic and compared seasonal figures or rates without accounting for site conditions. To address this shortcoming, an observational before–after study with the empirical Bayes technique was used to determine the effect of FAST systems on crash frequencies. The results revealed that at sites where crashes were reduced, FAST systems contributed to an annual reduction of 2% on multilane rural highways, 16% to 70% on urban Interstates, 31% to 57% on rural Interstates, and 19% to 40% on interchange ramps between Interstates. However, at some sites, safety deteriorated with an increase in crashes. Although the precise causes of such increases are not completely clear, they may have been the result of increased traffic, systems not being maintained properly, or systems applying fluids in improper amounts or at the wrong time. On the basis of the collective results, high-traffic, high-crash severity locations are most suitable for FAST deployment.