During the 20th century, there has been a shift away from rail and water transport in favour of road and air. The single most dramatic change has been the rise in personal mobility in developed countries, encouraged by cheap oil, affordable motor cars and lifestyles built around commuting, out-of-town shopping, dispersed families and leisure activities. Since World War II, the number of vehicles on the road has risen from about 40 million to some 680 million. The fastest growth is now found in the developing world, though car ownership is still low. There will be more than 1 000 million vehicles on the road by 2025.
The trend away from public transport to privately owned cars is universal. Major metropolitan areas will soon reach a point of inability to sustain traffic. Many cities already have inadequate parking. Inadequate public transport and restrictions on private automobile use will mean a loss of mobility and forced decentralization. Transportation development policies and investments in most developing countries are focused on encouraging motorization which increases the dependency on imported oil to fuel motorized transport.