In the UK National Policy for Green Belts was included within the National Planning Policy Framework (NPPF). There were five purposes of Green Belt:
To check the unrestricted sprawl of large built-up areas;
To prevent neighbouring towns merging into one another;
To assist in safeguarding the countryside from encroachment;
To preserve the setting and special character of historic towns; and
To assist in urban regeneration, by encouraging the recycling of derelict and other urban land.
In addition it was widely recognised that Green Belt should increase access to the countryside, and that Green Belt boundaries should be ‘defensible’, i.e. marked by clear landscape features not vulnerable to development pressures. Previous piecemeal development of settlement edges had contributed to sprawl, sometimes cause towns to merge, and encroach into the countryside. It also moved the countryside further from the people. Where New Green Towns of Connected Cities were developed in what was previously the Green Belt they were always in carefully selected new locations so that they did not cause sprawl, the merger of towns or impact upon the setting of historic towns. They were also confined to defensible boundaries. The new settlements inevitably cause physical encroachment into the countryside, but to a much lesser degree than the same amount of development on a settlement edge. And most importantly, they were located to maximise sustainable transport and minimise car use.