Mobility is an important factor in road safety research, because it has a major influence on the number of road crashes and road casualties. Developments in mobility are determined by developments in, broadly speaking, four areas: demography, social culture, the economy, and spatial planning. Mobility in the Netherlands has been increasing since the 1950s. Today, more than 200 billion km are travelled each year. The increase in mobility in this whole period of time is due almost entirely to the car. Clear changes in this trend can be seen in the last ten years. Total annual mobility has still increased in the last ten years for the population group above the age of 40, whereas, conversely, it has decreased for the group below that age. This difference is largely the result of changes in the composition of the population.