Although road safety has steadily improved in Finland over the past few years, accidents in winter conditions still account for 25% of all fatal accidents. The primary winter maintenance measures are salting, sanding and snow removal. The present weather warning procedure is efficient but takes time. To reduce this time, warning systems using Variable Message Signs (VMS) were tested. Best signs were found to be the slippery road pictogram with a snow flake icon and the recommended distance headway sign. The system was implemented at three problem locations in Turku district. Speed and headway data were collected automatically on a vehicle by vehicle basis. These data were integrated with road condition data. Subsequent interviews showed 70% of the drivers understood the signs; 50% slowed down, the other 50% were already driving slowly. Speeds were reduced by 1.1-4.6 km/h. Examination of headway distribution showed that headways below 1.5s accounted for 25-35% in good conditions and 16-28% in slippery conditions. VMS signs were well understood, although many drivers did not understand difference between steady and flashing lights. They are essentially intended for sites of exceptional weather and road conditions; other systems should be used for areawide problems. Further studies are needed regarding novelty effects etc.
Abstract