Many people are surprised by the relatively small share of urban passenger travel made on public transport in Australia. Notwithstanding a slight narrowing of the gap in recent years, cars still dominate travel in capital cities, accounting for 85% of all motorised travel in Sydney, 89% in Melbourne and 90% in Brisbane. Their share in Perth and Adelaide is about 93%.

While there are several reasons for public transport’s low mode share, a key reason is it serves a small number of destinations — mainly the CBD — really well, but generally fails miserably for those travellers who want to go elsewhere, especially the great majority who want to travel between suburbs.

The “hub and spoke” pattern was fine 100 years ago, but now most destinations and origins are highly dispersed. For example, only about 10% of all jobs in Sydney and Melbourne are located in the CBD and a clear majority are more than 10 kilometres from the centre. Also, fewer than 10% of residents live within five kilometres of the centre.

As a consequence of this out-moded form, using public transport to travel across suburbs is often excruciatingly slow. In many cases services are infrequent, operate on restricted hours and require intolerable waits between connections. Where they exist, cross suburban services follow seemingly capricious timetables and tortuously circuitous routes.

Much needs to be done at the political and technical levels to address these problems. One important approach is the idea of a “synergistic” public transport system (or “networked”, or “connected”, or “multi-directional”). It conceives the entire public transport system as an entity — a network — rather than as a series of isolated “lines”.

In conceptual terms, the idea involves a backbone grid of very high quality public transport services operating across the metropolitan area of a city. Imagine a series of parallel north-south services overlain by a similar sequence of parallel east-west services, all operating at high frequencies until at least the early hours. Because Australia’s large cities have legacy radial train systems, the grid is likely to look more like a spider’s web than an orthogonal network — while that’s imperfect, the idea is essentially the same.

The grid must be dense enough that passengers can get to it easily from their origin or destination, ideally by walking. Once they’re on it, they can transfer between services at each node, giving them the ability to go “from anywhere to anywhere at any time” rather than just to the CBD.

The synergistic value of the grid lies in connections. But to be attractive, transfers must be as painless as possible. That means a single fare irrespective of the number of transfers; short waiting times in a pleasant and safe environment; and easy physical access between modes — the idea of crossing a major road to get from the station to the bus is anathema.

In particular, timetables either have to be co-ordinated (which is technically hard) or, preferably, services have to be so frequent that passengers don’t need to bother about timetables. Most practitioners think the minimum is an average wait of five minutes with a maximum of 10 minutes.

I’ve described the high-level concept. In reality, cities differ — some have large water bodies, hills and higgledy-piggledy street layouts that mean only an approximation of a grid will be feasible (sounds like inner-city Sydney). It’s likely the orbital services will mostly be provided by buses operating on existing roads rather than by light rail or bus rapid transit services with their own dedicated right-of-way.

It’s also probable the grid will have a hierarchy in service quality, with some services in areas of low patronage potential operating at lower frequencies. Moreover, several origins and destinations will test the idea of what’s a reasonable walking distance, with some patrons relying on feeder buses to get to their nearest station.

Nevertheless, this is a valuable aspirational model that sets a direction for long-term planning. But it has considerable value now. For example, it suggests it’s worth asking if investing billions in new radial rail lines to carry small numbers of people from the suburbs to the CBD (e.g. proposals for new Rowville and Doncaster rail lines in Melbourne) is the wisest use of scarce transport dollars. Perhaps they’d be better spent on enhancing the connectivity of the public transport system so as to create a real, synergistic network.

*Read the full story at Crikey‘s new blog The Urbanist