Dynamic Modeling of Winter Maintenance Strategies and Their Impact on Skid Resistance

Abstract

Snow and ice during the winter period is one of the main factors for low skid resistance resulting in elevated road accident levels and economic cost. Winter maintenance with the application of sodium chloride causes ecological damage due to chloride in road run-off. However these salt application in combination with snow ploughing is, for lack of alternatives, the weapon of choice for road authorities in order to maintain safe roads. The timing and amount of scattered de-icing agents, e.g. sodium chloride, is commonly decided by the winter service vehicle driver based on experience and/or rigid tables. With this common neglect of the variable environmental factors such as traffic intensity, precipitation, surface temperature and gradient, suboptimal results are very likely. Based on an intense research program and statistical analysis funded by all regional and national road authorities in Austria, a model to simulate the impact of these factors on skid resistance was developed. The key factor is the determination of the residual salt depending on traffic and precipitation over time, resulting in an increased freezing point of water on the road. The goal of salting is to lower the freezing point of the brine on the road below surface temperature, thus preventing freezing with significantly lowered skid resistance. Based on the presented model, it is possible to simulate the impact of winter maintenance and optimize the timing and amount of applied de-icing agents under any condition over time. Excessive or unnecessary treatments can be detected in the simulation process and therefore be eliminated by specific instructions leading to optimized winter maintenance with decreasing costs, ecological damage and consumption of resources without lowering the level of safety.