Winter model : road condition submodel

The road condition model presented in this paper is a submodel in the Swedish winter maintenance management system, the Winter Model. The Winter Model will make it possible to asses the most important effects and their monetary value of changes in winter maintenance strategies and operations in Sweden. The effects are assessed for road users, road administrators, and the environment. The submodel road condition modelis the central part of the Winter Model. The road condition model will characterize the state of a winter in terms of a road condition description hour by hour. The road condition modelprovides input data for other models where different effects such as accident risk, travel time, fuel consumption, road management costs, and environmental effects are assessed. In the first stage we have developed a model that will describe how road conditions are affected by weather, maintenance measures taken, and traffic on two-lane rural roads with a width of 7 to 9 m and speed limit of 90 km/h. To a great extent, the basis for developing the road condition model will be data already collected from nine observation sites, during one or two winter seasons, with the purpose of developing another submodel of the Winter Model, the accessibility model. For several periods, data from these observation sites contain information hour by hour regarding weather, traffic flow, initial road condition, and maintenance measures taken. Also specified types of road condition development—mainly connected with snowplowing and anti-icing treatment—can be studied. Additional information has been collected in special field surveys from the winter of 2002–2003. One survey covers the development of ruts down to the pavement in hard-packed snow or thick ice, caused by vehicles with studded tires. Also the mechanism for a wet or moist road to dry out has been studied. The road condition model will initially consist of the following nine submodels. The first five submodels are related to measures and the last four to traffic and weather: (a) anti-icing treatment, (b) snowplowing combined with anti-icing treatment, (c) snowplowing, (d) gritting, (e) grading, (f) rut development in hard-packed snow or thick ice, (g) condensation, (h) splashing from a wet road, and (i) drying of a moist road.