I refer to the report headlined ' 'Make idle land HK's New Jersey' ' (Sunday Morning Post, July 14), regarding the rezoning of farm and recreation land in the New Territories. I was appalled by Urban Watch chairman Wong Wah-sang's suggestion that people could work in urban areas in 'high rises in Kowloon and on Hong Kong Island and return home to their nice low-rise houses in the New Territories, just as people do in New York and New Jersey'. Doesn't he realise that the commute between New York City and New Jersey causes major traffic jams to and from the Big Apple every day? Besides the inconvenience and travelling time, the additional traffic generated between the New Territories and urban areas in Kowloon and Hong Kong Island adds to the already unbearable air pollution problem due to exhaust fumes from vehicles. What is needed to achieve sustainability in a city is diversity. One way of achieving this is by having strategically planned mixed-zone areas so that people could work, shop or participate in recreational activities within walking distance of their homes. In major cities such as Tokyo, there are even proposals for mega-structures where different areas for commercial, office, recreational and residential use can all be housed in the same building. These schemes are designed to counter the kind of urban sprawl created by the urban-suburban division. I am surprised that Mr Wong would propose a backward step which is contrary to the principles of sustainable development. JOSEPH WONG Lecturer Division of Building Science and Technology City University of Hong Kong