Driving behaviour in fog : analysis of inductive loop data

A study on longitudinal driving behaviour on motorways in fog has been carried out based on an analysis of real traffic data. Traffic data were available for a period of over one year on an individual vehicle level. They were obtained from inductive loop detectors on a two-lane motorway near the city of Breda, The Netherlands. These data obtained with detailed visibility measurements from a sensor near ther road. Results show that drivers reduce their free driving speed in fog, but not sufficiently to avoid a collision when they would be confronted with a staionary or much slower lead vehicle. The most criticle behaviour was displayed in the visisbility range between about 40 and 100 m.