Typical suburban development, with its private lots opening off streets, almost confines children to their houses. Many urban settings are much worse. Parents, afraid of traffic or of their neighbours, keep their small children indoors or in their own gardens. Thus the children have few chance meetings with other children of their own age which enable them to form the groups essential to a healthy emotional development. This tendency to isolation is increasingly the case in modern urban environments.
A 1993 UK report found that the most restricted children were those who lived in suburban areas. Adults' fear, and their dependency on the car, has resulted in virtual imprisonment for many children. Inner-city "deprived" areas had their own problems of lack of child play areas, dirty playgrounds, or play areas that are sterile hard tarmac or concrete, which limit the type of recreation options.
If children don't play enough with other children during the first five years of life, the chance is greater that they will have some kind of mental illness later in their lives. Since the layout of the land between the houses in a neighbourhood virtually controls the formation of play groups, it therefore has a critical effect on people's mental health.