To address weather-related accidents on I-90 near Vantage, Washington, the Washington State DOT (WSDOT) assessed the benefits and costs of deploying an automated anti-icing system to prevent the formation of pavement frost and black ice and to reduce the impact of freezing rain. Based on accident history over a 3-year period for the I-90/SR 26 Interchange area, poor road surface conditions contributed to 42 percent of total accidents and 70 percent of winter accidents. The high-accident corridor includes a 955-foot radius horizontal curve and a vertical alignment transition from three to five percent within the limits of the curve.

The proposed installation consists of a liquid chemical storage tank, a pump, a dispensing system with spray nozzles, an environmental sensing station (ESS), a computerized control system, and a closed circuit television (CCTV) camera for remote viewing. The initial cost estimate was $599,500 (1999). The control system monitors weather and road condition data from the ESS, and automatically activates the dispensing system when predetermined conditions exist. The system also alerts dispatchers and the maintenance supervisor when the anti-icing system is activated. Annual O&M costs were estimated at $32,800 (1999). Costs data used by WSDOT for the analysis are excerpted from the source report and presented below.

The present worth of benefits, present worth of costs, and benefit-to-cost ratio are calculated using the WSDOT Benefit/Cost Worksheet for Collision Reduction. The analysis yielded a benefit-to-cost ratio of 2.36 indicating the viability of the proposed solution.