Sustainability requires the balancing of the needs for land for development with the amount of land available. Large populations place significant stresses on available land, with natural habitats frequently given over to agriculture and urban development. In modern times the introduction of the motor car has allowed populations to slowly spread outwards from existing urban centres. Dispersal has occurred as people looked for cleaner environments to live and work in, away from busy town centres. As cars became more affordable, people were able to travel out of town easily. This in turn led to an increase in the length of journey that people made, and an increase in the number of cars on the road.
To relieve the pressure of transport on society and the environment, emphasis now needs to be placed on reversing the trend of population dispersal outwards from urban areas. By effective land use planning, activities including work, shopping and leisure are brought closer together. This would reduce journey distance to a level where travel on foot and by bicycle becomes more popular. To facilitate this, urban centres need to be made more attractive and the quality of urban living improved.