EFFECTS OF THE WEATHER-CONTROLLED TRAFFIC MANAGEMENT SYSTEM ON SINGLE-CARRIAGEWAY ROAD SECTION OF E18

A variable speed limit system controlled by weather and road condition data has been developed in Finland parallel to seasonally changing speed limits. The effects of variable speed limits has previously been investigated on the motorway section. This study was designed to investigate the effects of the variable speeds limit and messages on single-carriageway roads, a two-lane section and a semi-motorway section. The total length of the weather controlled road is currently 25 km. All 32 speed limit signs on the section are variable fibre optic signs. In addition there are eight variable message information and warning signs. The speed limits used on the section are 60 km/h, 80 km/h and 100 km/h. Data on driver behaviour were obtained from one measurement station on the undivided mixed traffic road and one measurement point on the semi-motorway. The data from the undivided mixed traffic road was used as control data for the undivided mixed traffic road in winter and for the semi-motorway in summer. The design was a before-after study with a control road.In conclusion, the effects of the system are as expected if the system is appropriately used. The increase in mean speed improved the fluency in good road conditions, probably with no detrimental side-effects. In adverse road conditions the lowered speed limit decreased the mean speed and headways between vehicles, which is desirable for traffic safety. In addition, the findings suggest that the use of variable speed limits calls for a sophisticated control system. Inadequate speed limits increased the mean speed excessively and decreased the headways substantially, thereby reducing traffic safety. The drivers accept variable speed limits and rely on the system. The study has been granted European Community financial aid in the field of Trans-European Networks - Transport.