Capital expenditure on motorways versus rail lines, Melbourne

The provenance of the exhibit above is uncertain (it’s from Twitter), but it purports to show how much was spent building new motorways in Melbourne over the last 50 or so years as compared to building new rail lines.

It shows rail has done very poorly on this measure compared to motorways. That’s undoubtedly true when evaluated in terms of kilometres built but I don’t think this perspective on infrastructure expenditure tells the full story.

There’re other issues that arguably should also be considered in evaluating the implications of the comparison, like the proportion of motorway kms funded by private investors; the relative mode shares of road and rail, both historical and prospective; the level of operating subsidy for rail; and expenditure on other trunk services like arterial roads, light rail/tram, and buses/BRT (e.g. see Do governments spend too much on roads?).

But I think it’s incomplete for another reason; it misunderstands and misrepresents the role of rail and leads to a false emphasis on extending coverage ahead of capacity as the measure of progress with rail. Here’s why.

High order transport infrastructure

Both rail lines and motorways are high order transport infrastructure; they provide a dedicated right of way for trunk services. They have limited access and grade separation from lesser networks so they can provide higher speed routes for longer trips.

They’re accordingly spaced out geographically and rely on travellers accessing them at strategic points by driving on regional or local roads (to get to motorway on-ramps) or by walking, catching feeder buses or driving cars (to get to rail stations).

In common with other Australian capital cities, Melbourne started to get serious about building motorways in the 1960s. However at that time the city already had an extensive and longstanding network of rail lines radiating from the CBD. These were mostly constructed in the nineteenth century and electrified by the 1930s. (1)

Thanks to this historical legacy, most Melburnians currently live within a comparable feeder catchment by bus or car of a rail line (although the Doncaster and Rowville regions are alleged “black holes”). In many cases feeder services to stations are poor but the potential exists to improve them at much lower cost than building another rail line.

In recent decades urban development has generally been directed to areas with existing rail lines or where rail lines have been extended (Sth Morang) or promised (Mernda).

Releasing rail capacity

What matters most with rail in a city like Melbourne isn’t extending the coverage of the existing rail network but increasing its capacity. Rail is mass transit; its great advantage over roads is its ability to carry huge numbers of passengers before it becomes fully congested.

It works because it collects passengers within an extensive catchment and concentrates them spatially and temporally; its high capacity justifies having a dedicated right of way. Relative to the population of travellers in the suburbia typical of Australian cities, rail therefore necessarily has a “sparse” network supported by feeder services.

Given the existing network, the focus for investment in rail in a city like Melbourne needs to be on increasing capacity (really, it’s releasing capacity), especially via measures to increase the frequency of rail services.

That means prioritising expenditure on, for example, procuring more rolling stock, modernising signalling, duplicating and upgrading track, removing level crossings, improving coordination of services, providing efficient feeder services, and more.

Occasionally it will also require building some relatively short new rail lines like the Melbourne Metro CBD tunnel; but the primary objective of the Metro (and comparable CBD tunnels proposed for Brisbane and Sydney) is expanding capacity and improving reliability of the metropolitan network, not extending its coverage. (2)

Comparisons like that in the exhibit need to take account of all the funding spent on improving the capacity of the urban rail system. By the same token it should also include expenditure on all measures to increase the capacity of existing motorways e.g. widenings, metered entry.

It’s not just coverage

Even looked at in this broader way, I expect that expenditure on motorways in Melbourne would still well and truly surpass that on rail over the last 50 years. (3)

But focussing solely or primarily on expanding rail coverage is not only limiting, in the case of Melbourne it implies poor investment decisions. For example, as I’ve explained before, building new rail lines to Doncaster and Rowville at this time would be extremely poor public policy.

And by itself, comparing road and rail expenditure isn’t necessarily a good measure of how much is being achieved. The great virtue of rail is the huge level of latent capacity if offers; in many cases it can be tapped at relatively modest cost compared to increasing the capacity of roads e.g. by buying an extra train or improving coordination with feeder buses. (4)

The priority for additional suburban rail coverage might be higher in some cities than it is in Melbourne, but in general the measure of how well Australian cities are doing in improving public transport isn’t just a matter of how many extra kilometres of new rail lines are built to extend coverage; what’s at least as important is how much extra capacity, reliability and connectivity is provided in the public transport system as a whole.


  1. In the nineteenth century, rail lines in Melbourne were initially mostly financed by private investors (usually unsuccessfully) and subsequently mostly by speculative and corrupt government expenditure that had little real social justification at the time (see What can history teach us about rail?)
  2. The new stations envisaged at Parkville, Arden and Domain as part of Melbourne Metro will be valuable, but they’re essentially a by-product; the key purpose of the project is to increase the capacity of the network and improve its reliability.
  3. Although note that when looked at nationally and for a brief period up to around 2010, the level of expenditure on major rail and road infrastructure was roughly equal.
  4. That’s true of roads too but only if the public is prepared to accept measures like congestion pricing; so far that seems highly unlikely except (perhaps) in city centres.