The large-scale project, the Winter Model, will result in a model for assessing the most important effects and their monetary value of changes of winter maintenance strategies and operations. The winter road condition model is 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 model provides input data for the other models where different effects such as accident risk, travel time, fuel consumption, and environmental effects are assessed. In the first stage we intend to develop a model that describes 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 winter road condition model will be data already collected from nine observation sites with the purpose of developing the accessibility model. For several periods data from these observation sites contain information hour by hour regarding weather, traffic flow, initial road condition, maintenance measures taken and specified types of road condition development mainly connected with snow ploughing and anti-icing measures. Additional information, mostly development of ruts down to the pavement in hard-packed snow or thick ice caused by vehicles with studded tyres, and conditions for a wet or moist road to dry out will be collected by field studies as from the winter season 2002-2003.