Sorry for the hoary cliché but I really do think it’s time for a new way of thinking about public transport.

Much of the debate on transport in cities is too simplistic. All too frequently it’s reduced to a simple nostrum: “replace all car travel with public transport”. I think it’s more complex than that and, to use another cliché, requires a more nuanced approach.

Let me be clear from the outset that there are compelling reasons why we need to invest more in public transport — for example, to provide mobility for those without access to a car. Another reason is to provide an alternative to roads that are becoming increasingly congested.

But I’m not convinced that the reason most commonly advanced — to overcome the environmental disadvantages of cars — is all that persuasive. Here’s why.

There is considerable scope to make driving “greener”. Petrol is like water. It’s so cheap that too many of us use it profligately, but given the right behavioural incentives we could use considerably less without materially lowering our standard of living.

There’s also room to increase the fuel efficiency of existing internal combustion engine technology and to reduce the weight and speed of cars. Then there’re alternative fuels such as compressed gas and ethanol and whole new technologies such as cars powered by electricity and hydrogen.

There are issues here — electricity in Australia is dirty, there are environmental issues around batteries, ethanol potentially competes with food for agricultural land and it could take considerable time to turn over the national car fleet.

But as I’ve argued before the attractiveness of the car and the value of the existing infrastructure should not be underestimated as forces of change. The major car companies are now the world’s biggest R&D spenders.

Another consideration is that public transport is not as green as it is commonly assumed. It is only fuel-efficient and emissions-efficient if it has high load factors like it does at peak hours, but the requirement to run in off-peak times, especially at night and on weekends, dilutes this advantage substantially.

As Victoria’s Commissioner for Environmental Sustainability observed, modes that rely on coal-fired electricity, such as Victoria’s trams and trains, “have GHG full fuel cycle intensity levels on an average per person-kilometre basis that are comparable to motor vehicles”. As this report prepared for the 2008 Victorian Climate Change Summit shows, the GHG intensity of buses in Victoria is in fact worse than that of cars.

This would not be a problem if the vast bulk of all future trips were made by public transport. But in Melbourne the government’s target is for public transport to capture 20% of motorised travel by 2020 and in Sydney the target set by the Independent Inquiry is 28% of motorised travel by 2036.

That’s not all though — the lion’s share of these ambitious increases would almost certainly be in peak periods rather than the off peak.

The environmental justification for public transport is captured in the commonly accepted assumption that it must be provided on a scale and of a quality that provides a viable alternative to the car i.e. it has to offer a level of service that is superior to the car. This leads to serious proposals like having a system that provides “every 10 minutes to everywhere” so that residents, theoretically, never need to even own a car.

I can’t see that 10-minute frequencies would be attractive enough, other than in areas such as the CBD, to make many car owners leave their vehicles in the garage, but of course it would be wonderful to have. However, the key issue is that these sorts of aspirational goals need to be set in the context of the enormous financial task involved not just in providing better public transport but in providing it on a scale and of a quality that can out-compete cars.

My view is that policy on public transport investment should stop trying to out-compete the car. This is a near impossible task in most parts of the metropolitan area and is very probably unnecessary on environmental grounds. There should instead be two key focuses.

The first should be on the highly concentrated parts of metropolitan areas such as the city centre, where congestion is increasingly rendering the car uncompetitive. These are the locations where high standards of service are justified and where public transport really does out-compete the car.

But that’s still a relatively small part of our cities — in Melbourne’s case, the area within five kilometres of Melbourne Town Hall accommodates less than 10% of the metropolitan population and less than 30% of jobs. And jobs in turn only account for about 30% of all travel within the metropolitan area. If cars are “green” then a large part of the warrant for public transport in non-concentrated areas is removed.

The second focus should be on providing mobility for those without access to a car. I concede I don’t know what a minimum acceptable level of public transport service is for this group — that’s an interesting question in itself. But I’m pretty confident it would cost a lot less than what would be required to make travellers who aren’t going to the city centre abandon their cars and switch to public transport.

Providing sustainable and workable transport within our major cities is going to be a long and difficult task. I think it makes more sense to recognise that we actually need the car to keep our relatively low density cities (at least by European standards) functioning for many decades to come. Yes, even green cars have negatives, but we should focus on ways of civilising the beast.

Investment in public transport needs to be strategic and targeted, not sprayed across-the-board. There are other socially worthy uses for scarce funds. The “green” argument is the weakest rationale for more public transport.

This first appeared on the Melbourne Urbanist blog site.