Analysing the effect of foggy weather on drivers' speed choice in two-lane highways

Foggy weather can reduce visibility for drivers and one of the main consequences of this condition can be the change in behaviour regarding choice of speed, which will vary from driver to driver owing to their varying personal and socio-economic characteristics and driving experience. The aim of this study is to assess the effects of adverse weather conditions on speed-choice behaviour of drivers on a two-lane rural highway. Using a driving simulator, speed-choice behaviours of more than 75 licensed drivers/attendees were evaluated in six different weather scenarios. The socioeconomic characteristics of drivers as well as their driving records (including accident rates) were also gathered. Using a binary logit model, the probability of choosing speeds faster than the 85th percentile speed was estimated. Light and heavy fog, driving experience and the rate of accident involvement were found to be significant as negative factors for speeding. In addition, it was found that the various speeds chosen by drivers were all reduced significantly in low lighting conditions, which might be a positive safety measure under such conditions.