Common land has two specific social functions. First, the land makes it possible for people to feel comfortable outside their buildings and their private territory, and therefore allows them to feel connected to the larger social system - though not necessarily to any specific neighbour. And second, common land acts as a meeting place for people. In pre-industrial societies, common land between houses and workshops existed automatically; but in a society with cars and trucks, the common land which could play an effective social role in knitting people together no longer occurs in this way. There is an argument that agoraphobia is increased among city dwellers by their lack of common land (people may feel that they have no 'right' to be outside their own territories). In fact, estimates suggest that the amount of common land needed in a neighbourhood is about 25% of the land held privately. This is enough to provide a meeting ground for the people who live in the vicinity, to contain children's games and to give a meeting place for mothers where, on a good day, they might come together under a big tree or a pergola, to sew or gossip, while their infants sleep in a pram or their runabout children grub around in a play pit.