Traffic psychology theories : towards understanding driving behaviour and safety efforts.

It is an often presented view that the theory development in traffic psychology has not proceeded very well during recent decades. Especially, testable hypotheses have not been drawn from theories, which also means that alternative theories cannot be put into test. Useful taxonomies have been presented, however. Among the most influential ones, the hierarchical structure of driving task is now generally understood, being helpful in structuring driver skills and mechanisms that affect exposure to risk and accident output of the system.Driver education is one field which has obviously benefited from better structured taxonomies. Such a hierarchical structure, together with a detailed taxonomy of on-road control tasks and respective exposure, is also a necessary tool for understanding accident loss as related to exposure to risk. What is needed, however,is truly functional models which predict dynamic road user behaviour on road. Good progress has been made in modelling certain partial tasks.It has been shown, for example, that drivers are not simple servomechanisms who keep the car in the middle of lane and continually correct smallestdeviations.The present work, a conclusion of the Symposium on Traffic psychology theories in ICTTP 2004, a challenging task in searching for more general mechanisms which explain drivers' dynamic behaviour.What actually guides a driver in traffic? What are the basic mechanisms that, for example, determine drivers' moment-to-moment speed control, in different environments,as restricted by speed limits or not..This study concentrated on motor vehicle drivers, well knowing that the same brains, and largely the same cognition and emotions guide us as a pedestrian and bicyclist. However,as related to the taxonomies mentioned above,it should be to predict how different possible hierarchical levels influence each other; how on-road driving experiences translate to travel choices, e.g. when older people reduce driving at night or in impaired weather conditions. This, and the search for general pacing factors, is very much related to a challenge for traffic psychology: what actually determines the effectiveness of transport system modifications?