Is decentralisation the answer to cities that are 'too big'?

Where regional cities have grown strongly – like Cairns – it's because there's demand, not because of some policy intervention to make it grow (although government has a role in facilitating – or stopping – underlying demand).

So what's going on here? The nub of the issue is this debate isn't about regional development; rather, it's about the idea of sending Melbourne's population growth to regional dormitory suburbs instead of fringe suburbs. It's the same idea as Plan Melbourne promotes i.e. substituting regional sprawl for suburban sprawl.

Is regional sprawl a better idea than fringe sprawl? It's a plausible strategy. London, for example, has around forty 'overspill' or satellite towns like Hemel Hempstead and Milton Keynes lying beyond the green belt and housing 4 million residents. They're closely tied economically to the centre; they're London's outer suburbs in the same way as Melton and Sunbury are Melbourne's fringe suburbs.

Regional sprawl could provide benefits to regional centres:

• Faster transport connections between regional cities and Melbourne would increase the locational choices of those working in the capital and enhance the access of regional residents to Melbourne's attractions and specialised services.
• All those new dormitory residents would create jobs in population-serving industries for regional cities e.g. tradies, fast food workers, teachers. That would help retain young people who currently leave for the big smoke.

On the other hand, regional sprawl could have some disadvantages compared to fringe sprawl:

• It would require seriously expensive trunk transport infrastructure to get workers from their regional town to their jobs and other services (like the airport) in Melbourne.
• There's no infrastructure saving. Limited existing "spare capacity" in services in regional cities would soon be used up. The loss of economies of scale in the supply of services like health, education, water supply and sewage treatment, might increase costs.
• The pressure to increase residential densities and reduce car use would be lower in small cities compared to Melbourne's fringe because accessibility is greater.
• Many long distance non-work trips to Melbourne and a significant proportion of commutes (not all regional commuters would work in the city centre) would inevitably end up being made by car because it provides flexibility at the destination.
• The environmental impact could be worse, given much of the land around Melbourne's north and west – where most future suburban growth is expected – is already degraded.
• Melbourne businesses located outside the city centre might not get the same benefits from a larger labour market than they would if population growth took place on the suburban fringe.

The case hasn't been made that Melbourne is or will be "too big". There are plenty of successful cities in the world that are much bigger than Melbourne is forecast to be by the middle of the century (see also Will Sydney and Melbourne implode as they get bigger and bigger?).

Melbourne needs what all growth requires; better infrastructure and better management (and let's not forget long-term population forecasts have a poor record for accuracy).

Although it's already a core component of Plan Melbourne, the regional sprawl scenario is barely understood in terms of its benefits and costs compared to fringe sprawl. A lot more hard-nosed analysis is required.