Is Melbourne’s promised loop rail line justified by jobs growth in suburban centres?

More recently, the suburbs have lost out to the inner city notwithstanding spectacular population growth across Melbourne as a whole. The proportion of jobs within 4 km of the centre increased from 26% in 2006 to 28% in 2016. The proportion of jobs in the suburbs correspondingly declined and, importantly, the share of metro jobs in major suburban centres remained static at 5% over the period.

The growth of the inner city reflects the continuing transition to the knowledge economy and the importance of factors like the demand for face-to-face contact in business. While Melbourne's suburban centres remain important places for local population-serving businesses and space-intensive industries, they aren't proving attractive for firms that value the level of density that justifies mass transit. They have better options.

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Melbourne isn't a polycentric city; rather, it's mostly a dispersed city. It has a dominant inner city with 28% of jobs, but the great bulk of employment – 72% – is in the suburbs. And contrary to the received wisdom, 93% of those suburban jobs are scattered; only a small fraction of suburban jobs are in major suburban centres (just 7%; or 5% of metro jobs).

Costly high-capacity systems like underground heavy rail make obvious sense in the CBD with its huge concentration of activities at very high densities. Commuting within Melbourne's geographically extensive suburbs, however, requires a transport system that deals more effectively with low levels of concentration than mass transit. That's been the domain of unrestricted car use, but with increasing congestion there's a pressing need for other solutions, like road pricing and more flexible transit systems (e.g. see Isn't there a much, much better way to do cross-city public transport?).

There might be other justifications for spending $50 billion on a suburban loop rail line (although I think that's questionable – see Has Daniel Andrews gone loopy on rail?), but it's doubtful if growing suburban centres is one of them.