Evaluation of fog-detection and advisory-speed system

The effectiveness of automated fog-warning system and advisory-speed system on driver behavior regarding speed on highway during foggy weather, was analyzed. The warning system includes visibility sensors that automatically activates a variable message sign that posts an advisory speed, responding to fog induced hazardous conditions. The data collected from 36,013 observations, included vehicle speed, volume, classification, time headway, time of day and visibility distance. It was found that fog visibility less than 50 m was the range that affected the drivers' behavior in the study sites. The results show that drivers reduce their speeds significantly when visibility distances is below 50 m.Wessex Institute of Technology, Southampton, U