The sustainable development imperative has revived a forgotten, or discredited, idea: that planning ought to be done, or can be done, on a big scale. Up to the 1960s planning had a long, and reasonably creditable, history of visionary ideas. After that date, the public lost confidence in planners, and planners lost confidence in themselves. Subsequently, pragmatism has ruled. However, there is now a fascinating debate underway about the role of planning in promoting sustainable development, and-here we have the big idea-about which urban forms will most effectively deliver greater environmental protection. Viewed as a narrow environmental debate, the issue is profoundly important. But when the broader economic, social and cultural repercussions are taken into account, it soon becomes apparent that nothing less than the future of western lifestyles is at stake.
This debate is not the preserve of unworldly academics. It is taking place at inter-governmental, governmental, and local government levels across the world. Following the Brundtland Commission report of 1987 (World Commission on Environment and Development, 1987), the notion that the natural environment should become a political priority-under the 'sustainable development' banner-has taken hold to a remarkable degree. In many countries there have been profound changes in policies and in political and popular attitudes, as commitment to the sustainable development idea has increased. The fundamental question in all places, however, has been how to deliver major environmental improvements. One common answer seems to be to use planning systems to achieve these gains; and, in turn, to use those planning systems to achieve greater urban compaction. Thus, a legitimate, indeed profound, research question is whether such compaction-'the compact city'-will deliver the gains demanded by the politicians.
The political urgency of this debate is demonstrated by the fact that we have a rare case of politicians racing ahead of academics, pressing for specific policies before the research community is able to say with any confidence which policies will have what effects. Perhaps this arises because national governments are