Driver behaviour in fog is not only a question of degraded visibility - A simulator study

The results showed that the drivers decreased their speed with decreasing visibility distance, i.e., speeds were slower in the 30 m-visibility conditions than in clear conditions; but, speeds on the two-lane motorway remained faster than on the two-lane rural road, even for the denser fog. In the 30 m-visibility condition, the faster speeds driven on motorways than on two-lane rural sections violated those advocated by the French Highway Code. The distances travelled in conjunction with the speeds driven according to the two-second rule revealed that HTs less than 2 s and small HDs do not necessarily match with hazardous driving.