The results of a 2-year project to investigate the feasibility of automatically detecting precipitation type for highway hazard-reduction programs in the Cascade Mountains of Washington State are reported. The project investigated available technology for remote identification of precipitation type, selected a suitable sensor for testing, and compared field and laboratory tests with visual observations. Modifications of the hardware and software were conducted to optimize the use of precipitation identification (PID) sensors in operational hazard-reduction programs.
A PID sensor was installed at the Washington State Department of Transportation (WSDOT) observation station at Snoqualmie Pass, and was connected to automatic data-logging equipment. Another PID was equipped for mobile use and tested at mountain sites in Alaska, other areas of Washington, and in Japan.
Data from each sensor were compared against visual observations. The results of this analysis showed adequate performance from the PID. The analysis also showed that the PID data can be a valuable asset to the hazard mitigation programs along mountain highways, particularly when combined with data-loggers, totaling precipitation gages, and computer graphics.