The system design included a liquid chemical storage tank, a pump, a 3,100-foot dispensing system with barrier-mounted and pavement-embedded spray nozzles, an environmental sensor station (ESS), a computerized control system, and a closed circuit television (CCTV) camera for remote viewing. 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 North Central Region maintenance supervisor when the anti-icing system is activated.
The present worth of costs, the present worth of benefits and the benefit-to-cost ratio were calculated with WSDOT’s Benefit/Cost Worksheet for Collision Reduction. Cost elements included design, construction, power and communication, operations and maintenance costs. Benefits were the estimated reduction in snow, ice, and wet pavement crashes. Using historical crash data, the annual rate of collisions over a three-year period was determined and compared to the expected rate of collisions after system implementation. It was estimated that 80 percent of the snow, ice, and wet pavement crashes would be eliminated (see key assumptions in notes below). The cost per collision was used to determine the annual safety benefit. The analysis resulted in a benefit-to-cost ratio of 2.36:1 with a net benefit of $1,179,274. This ratio validated the viability of the proposed solution. In addition to cost savings from crash reductions, WSDOT management expects that abrasive usage will be significantly reduced, resulting in lower cleanup costs and less damage to drainage structures. Improved level of service should also result from the deployment, enhancing mobility.
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