1 LEGAL MEANINGS AND DRIVERS’S INTERPRETATION OF ROAD

It is often claimed that road users have a poor knowledge of traffic rules and signs. Then, their behavior may vary from the expected behavior, producing misuses and accidents into the road network. From the point of view where road signs meaning is context-dependent, this paper is aimed at understanding how a loosing knowledge process can be built up during the driving experience. Contrary to novice drivers that learn the univocal meaning of road signs, expert drivers get low scores about the meaning of road panels that are made of icons and of graphic signs. This is a surprising case of practice lessening performance. We argue that the meaning of road signs is built in the context of the driver task and in the context of the current road situation. We have run an experiment that shows that expert drivers fail to the “what does it mean ” question when road signs are displayed in isolation or in the context of a real road situation, but they succeed to the “what to do ” questioning. We describe the whole set of 300 road signs both from their surface properties (form, color, icons, etc.) and from the required actions. The road signalization system appears to be a complex system that is not fully coherent since surface properties partially match the corresponding actions properties. Finally, we advocate tha