Road users are concerned by ice and snow on roads and streets. The main problems are increased accident risk and impaired accessibility. To prevent - or at least decrease - the difficulties, road administrators perform various maintenance actions. The actions are advantageous for the road users, but involve costs for the road administrators and negative effects for the environment. To optimize maintenance efforts the use of management systems should be applied. The Winter Model project will result in a model for assessing the most important effects and their monetary value of alterations of winter maintenance strategies and operations in Sweden. The effects are assessed for road users, road administrators, and environment. For the road users, the main effects comprise accessibility (in terms of vehicle speed and flow) and safety. By using simultaneous monitoring of road surface condition and traffic, the relationship between speed and different roadway conditions have been established. The speed reductions owing to 7 specified roadway conditions (moist, wet, ice or snow) relative to the speed at dry, bare conditions are generally significant. The reduction can be as large as 20 per cent. No relationship for traffic flow could be established. The average accident rate (accidents per million vehicle kilometers) during a winter season can be 16 times larger in black ice conditions than in dry road conditions. The accident rate in ice and snow conditions has an exponential relation to the duration of the condition, i.e. the shorter the duration, the higher the accident rate.