After years of doing hard graft on developing some sort of coherent, if often controversial, planning policy, South Australia’s Labor Party last week decided it would be much easier to flick the switch to populism.

You don’t need to be Ludwig Wittgenstein to see the inherent lack of logic in Labor’s policy thought bubble: leader Peter Malinauskas and his planning spokesman Tony Piccolo surely can’t believe their spin that mandating a minimum number of car parks in new developments will decrease congestion on local streets?

Labor has picked up on angst about urban infill and a subsequent increase in competition for on-street car parks. The disquiet is certainly real.

Their solution is a one-page “policy” which would see developers of new housing projects provide at least two off-street parking spaces for two-bedroom homes; one space for one-bedroom homes; and, if off-street parking isn’t possible, a site nearby for cars.

Consider, for just a few seconds, a multi-storey apartment development in the inner-city or CBD filled with, say 80 two-bedroom units, and you will immediately see the ridiculous impact such a policy would have on land use in Adelaide.

“Ludicrous,” is how Planning Institute president Kym Pryde puts it.

Pryde, like the Urban Development Institute of Australia and the Property Council, also flags another obvious flaw: a sensible policy position on planning can’t simply pull out one factor when, in relation to the built form, context is everything.

Labor can’t expect to be taken seriously on planning when it pushes a policy which would impact a McMansion on a giant outer suburban block in exactly the same way as a high-density block of flats next to a train station in the inner city.

In the case of the latter, Labor’s policy would seemingly require the developer to build a large car park, either on-site or nearby, to accommodate two spaces for each two-bedroom unit or above.

As Pryde says, such a move would require deeper excavation of underground carparks, intersecting with the water table and causing other logistical issues. Above-ground car parks in such circumstances are, most certainly, “not best practice”.

The other obvious flaw is that Labor’s policy is based on ignorance of empirical data and scant regard for fast-moving changes in both transport technology and human behaviour.

Victorian urban planning researcher Elizabeth Taylor has studied car parking policies and their impacts.

Writing in The Conversation, she makes this point: “Parking minimums are powerful tools for realising strategic urban plans − if, as was once true, the goal is maximising car traffic.”

So much for Labor’s claim that the measure will “reduce congestion on local streets”.

In fact, what Labor’s policy is likely to do is add countless hectares of expensive storage space to Adelaide, particularly if the party insists on applying its one-size-fits-all policy to the entire metropolitan area, including the CBD.

Surely, one of the reasons why people move to the inner-city and CBD – even in car-obsessed Adelaide – is to reduce the requirement for expensive cars and car parks?

The issue is more complex in the suburbs but, even there, the mix of housing and the urban context is surely something that needs to be considered, rather than applying blanket rules.

Why does this matter?

Because urban space isn’t unlimited – as we’re discovering in Adelaide. Changing planning policy to increase one particular land use – especially one devoted to cars, which stand idle for 95 per cent of their lives – means that the space can’t be used for other, potentially more useful, things.

As Pryde says, locking in car parking spaces across the city will essentially freeze out other, more sensible, options for urban transport.

It’s a familiar and intractable issue in Adelaide: while urban planners, including within government, understand completely that the only real way to reduce congestion is to dent Adelaide’s obsession with private vehicle transport, politicians and some loud voices in the mainstream media will not have it.

Anything that impedes a car is a social ill, in their blinkered, counter-productive, evidence-denying worldview.

There is a well-documented trend among young people away from car ownership: millennials are less likely to own a car than a previous generation. And it seems likely this trend will accelerate as car-sharing schemes, ride-share and, inevitably, driverless vehicles, increase in popularity. An increase in urban density will accentuate this move – one which Labor in SA once supported as a logical extension of its favoured transit-oriented developments – that is, developments that are located to actively reduce the need for car parks.

As just about every urban planner in Adelaide has repeated until they are blue in the face, this city’s ample, cheap car parking, its failure to invest in public transport, and its obsession with certain road-widening projects, will only increase the city’s traffic problems.

Something, at some stage, will have to give.

As Kym Pryde says, Labor’s proposal to mandate so much car parking reduces the flexibility to provide for other options for travel – options that will free up road space.

“Once that built form is there, it sets Adelaide into that,” she told InDaily. “I’m concerned with what that will mean.”

The other key point is that Labor has no evidence that building off-street car parks will actually get cars off the street, unless Malinauskas and Piccolo are planning to force councils to introduce new parking restrictions on local streets (and wouldn’t that go down well?).

“How you manage people’s behaviours so that people use car parking for car parking is something that needs to be considered,” Pryde says. “It will just become storage space.

“This needs a holistic view from a planning perspective.”

There’s nothing wrong with producing policy to address congestion and car parking concerns, but it needs to be part of a broadly considered plan that will address the wider issues.

Otherwise, it will be another shortsighted and expensive move which will either have no impact, other than increasing housing costs, or drive up the volume of traffic on our roads.

David Washington is editor of InDaily.