Sand and other abrasive materials are applied to icy or snow-packed roads to enhance traction in conditions where mechanical removal and chemical de-icing are not effective. A variety of methods have been proposed to optimize application rates and to develop end result specifications for winter maintenance. Laboratory and field test programs were undertaken to compare and evaluate these alternatives. A friction testing apparatus in a cold room laboratory was used initially to examine a broad range of application methods. Key results were then tested in field situations. The field program included development of methods to provide statistically reliable comparisons between sand types, application rates and methods. This involved characterization of the variability of friction and stopping distance on snow and ice covered surfaces, and estimation of vehicle stopping distances before and after material application. Sand application rate had the greatest effect on stopping distance, while sand size gradation and pre-wetting had little or no practical effect. Similar results were found in comparing the residual friction after exposure to traffic. This information provides a quantitative basis for establishing application standards and end result specifications for winter maintenance on public roads. (A)
Abstract