The development of Intelligent Transportation Systems (ITS) has caused road authorities to pay more attention to the provision of traffic information. New technology has produced smart sensors and automated data collection, modification and processing systems such as Road Weather Stations (RWSs). The Finnish Road Administration has adopted a policy to develop ITS applications gradually, using experimentation on a problem-driven as opposed to technology-driven bases. A significant problem in northern countries is the relatively high accident risk during slippery road conditions in winter. On the weather controlled E18 road in southeast Finland speed limits are controlled by data from unmanned RWSs. The speed limits are lowered automatically during adverse road conditions and in some cases signs for slippery road conditions are displayed as well. Six RWSs along this section collect standard meteorological data, which is fed automatically every 5 minutes to the central station for storage and analysis. This study of the two lane section of the roadway investigated the effects of dynamic speed limits and slippery warnings on driving speeds and headways. Driver acceptance of the weather-controlled road was also studied, and a reliability analysis was performed as well.