i've scoured the the technical professional press to find out if there is some general statement which sums up what sustainability means, and the one which i've seen most commonly referred to, i think, and the government has used it in this way, is a requirement to ensure the needs of the present generation are met in a way which does not prejudice future generations, now i do not believe that a properly conceived and located new settlement is any less sustainable in the long term that other forms of urban growth, and by properly conceived i've got to say i believe that to mean properly balanced er form of development for the new settlement, and i think i would say that new settlements have usually been proposed because continued infilling, like the the normal forms of accommodating further development requirements, infill, and peripheral development, have been determined in york context not to be sustainable, the sorts of issues which arise as a result erm of additional development in or on the edge of york and the surrounding villages, problems of additional congestion, loss of green space in towns, loss of employment opportunities and so on.