Frost frequently forms on roads and bridges during winters when the pavement temperature is at or below 273 K and below the dew-point temperature. Accurate forecasts of frost onset times, frost intensity, and frost disappearance help roadway maintenance personnel decide when, where, and how much frost-suppression chemicals should be used. A finite-difference program has been developed that predicts bridge surface temperature by simulating vertical heat transfer in a bridge in response to evolving weather conditions. A vapor flux calculation uses the bridge surface temperature and concurrent meteorological variables from a weather forecast model to produce forecasts of depth of frost deposited, melted, or sublimed. Comparisons of model results with measured surface temperatures from a Roadway Weather Information Systems (RWIS) station have demonstrated that the model realistically represents early-morning low temperatures and temperature trends when run with input from current observations. Average surface temperature error using observations was 0.25 K. Some of the error can be attributed to spatial separation of the bridge site and the radiation observation site. BridgeT is capable of supplying surface temperatures within 1K of measured values over a 40-hour forecast period if it is supplied with accurate weather forecasts.
