A driving simulator study was conducted to study the behavioural effects of signal changes of a fog signalling system. Fog signalling is an automatic system which in case of fog shows a speed limit to passing drivers that is adjusted to the visibility conditions. The signals as perceived by drivers may change in space (being confronted with different messages on subsequent signs) or in time (seeing a message change from one state to another while passing a sign). In the experiment, subjects drove in a simulated motorway environment with several fog scenarios, both with and without a fog warning system. The experiment consisted of two parts, dealing with signal changes in space and in time, respectively. This paper summarises the effects on free-driving speed found in both parts.
Abstract