In today's Age, you might have noticed an article on changes to Melbourne's Planning Scheme. For the first time ever, Melbourne has a clear idea of where its suburban boundaries will be. One of Melbourne's long-term problems is the sense that it could just expand north and east forever. So in part the changes are good: finally there's hard legislative planning to ensure that we can't create a megalopolis. This is a genuine change and one worth celebrating.

What seems to have grabbed the headlines is the idea that this imposes medium density living on the city. Which in a way is true, but not really news in that this process was well underway before the Planning Scheme was amended. Melbourne simply isn't sustainable at its current geographic growth rate.

It's also a little disingenuous to say that this will push house prices up. Melbourne has undergone in the last five years a long-term realignment in house prices. By providing a hard boundary on the city, it's true that densities will increase - if population growth continues, which is no certainty - and that this will increase house prices. But we already at the point of schism in Melbourne. Part of the reason we are growing at the edges so much is economic: it's much cheaper to subdivide large tracts at the fringe than redevelop existing suburban land. So rather than boundaries pushing prices, it's prices that have pushed the boundaries out.

The next interesting point concerns the green wedges. In fact, Melbourne has had a green wedge policy since the 1940s. The original planning concept was to ensure that Melbourne developed radially, with corridors of growth being separated by large undeveloped tracts of land to serve both as "lungs" and physical distinctions between suburban housing. This concept of development is actually quite closely tied to a railway model of transport - the lines of growth would actually follow railway lines outwards, a model pursued since the 1880s. The latter-day consequences of this can be seen in our ring roads, which attempt to link corridors. This development concept actually explains a great deal of why Melbourne looks like it does. Unlike Sydney, where such a radial pattern is made impossible by the coastal topography, Melbourne has from the start sought to have a hub by the bay and expand in spokes out from it.

Hence all our transport and our psycho-geography tends to separate in lines. We in the east don't know the west. If you know the east, you'll know a corridor from Prahran out to Glen Waverley, but not have much of an idea about Templestowe.

The interesting part about the green wedges is that they are being discussed again. In the 1990s, they were apparently regarded as legacy development concepts. They have been slowly whittled away over 50 years, and some of them are not much more than a third of their original size. My tip is to find some housing close to the edge of one, buy it and wait for the long-term appreciation.