ABSTRACT
The Greek philosopher Heraclitos once summarised his view on the world concisely in two words: ‘panta rei’, which means: everything is in motion. This statement seems to apply very well to our modern world, where mobility, interaction and communication have become a leading characteristic; motion is the driving force of progress. The increasing mobility (persons, goods) is also a worldwide source of much concern. Clearly, mobility is a ‘normal’ – and even positive – phenomenon in a growing economy; it may increase economic efficiency through the gains of trade and labour mobility and it also offers more social opportunities to all members of society through a better access to a wide variety of amenities. But there is a growing awareness that the positive effects of mobility are offset by negative externalities, such as environmental pollution, congestion or lack of accessibility, and high accident rates.
