Weather-controlled traffic signs

The new motorway Kotka-Hamina in Finland is about 12 km long. It crosses a small gulf of the sea, includes three junctions and will open in autumn 1994. Variable signs have already been taken into account when planning the road and the cables and signs will be installed to all junctions before the road is open. Two automatic road weather stations and one or two traffic stations will be installed. The outstations have several road surface sensors which measure road conditions both on the road section going over the gulf and on the road over the ground. Speed limit signs placed before and between the junctions are controlled automatically according to information collected from road weather stations. Results of research carried out in the winter of 1992-1993 define the logic that controls speed limits.