London is drifting towards becoming a road city, a kind of Birmingham of the south. Boris Johnson, the departing mayor, has set in motion “irreversible” projects to build new urban motorways crossing the River Thames in east and south-east London; a new subterranean ring road is also on the cards. In parallel with this, London is facing an air pollution public health crisis, with a Supreme Court ruling that the government and mayor must act upon.

The capital is a walking and cycling city. Rates of car ownership are falling. Public transport is bursting at the seams. So why are we committed to building new roads? Because of population growth, because there is a gap in the road network, claim Transport for London (TfL). It is true the population of London is growing, and more people have to travel further to their work – but there is no evidence all those extra journeys need to happen by car.

TfL has perhaps got to grips with the theory of induced demand whereby if you build a new road, more drivers will appear to use it – so many people, in fact, that the new road ends up with more congestion that you started with. Instead of one congested and polluting road, you now have two. Money well spent.

Source: Campaign for Better Transport.

But instead of learning the lesson that roads equal pollution and congestion, TfL hope that an even bigger splurge on road building – “package”, in their language – will allow them to do what no new road building scheme has ever managed to do. It is TfL’s belief that by building three new roads, then traffic congestion will be cut.

So what are we getting for our £2.25bn of tax-payer money?

The most advanced scheme is a proposed new tunnel next the existing Blackwall Tunnel. This has been given NSIP status – a nationally significant infrastructure project – that ensures a fast track route through the planning system. The scheme is supposed to provide economic benefit, but does nothing to connect the 10,000 new homes planned for the Greenwich Peninsula with jobs in Canary Wharf. A pedestrian and cycle bridge would be a more sustainable solution here, and would help people cross the river without getting in a car.

Source: Campaign for Better Transport.

The brilliant No to Silvertown Tunnel campaign have been very good at pointing out the flaws of the scheme, including the terrible air pollution levels that already exist in the area: these reach as high as twice the legal limit in some places. There is a story spread by some who fancy the idea of new roads, that if we build more urban motorways the pollution will vanish as traffic becomes more “free flowing”. But the evidence, which has been building since 1925, tells us that new roads equal more car journeys and increased congestion.

Surely the other schemes can’t be quite so bad?

Further east two new bridges are proposed. One of them, the Gallions Crossing, we’ve seen before as the Thames Gateway Bridge between Beckton and Thamesmead. It was a scheme so terrible that, in 2007, the planning inspector found that it would cause increased congestion, that it would be unsuitable for pedestrians and cyclists, that it would make air and noise pollution worse. He also found there is no evidence that regeneration and economic improvement would result from it. It failed on all the things it was supposed to do.

The third crossing is planned to connect Rainham with Belvedere, half way between Gallions Reach and the existing Dartford mega-crossing of two tunnels and a bridge. Transport for London in their own technical report have found it would cause the local road network to become congested with new traffic, that traffic pollution and noise would increase, and there could be a negative impact on the Crossness Nature Reserve and Rainham Marsh sites. Sounds great, yes?

Another argument for these crossings is that they plug gaps in the road network. But especially in outer London, the gaps in public transport crossings are just as wide. There is just one public transport proposal that Transport for London are taking seriously to plug one of these gaps: this is the London Overground extension from Barking to Thamesmead. But the current plan is this would be built after all the road crossings, in 2025.

Did I mention London is in a public health crisis over air pollution?

As Birmingham is removing some of its urban motorways, we need more sustainable public transport plans in the capital, and not a package of expensive and polluting roads that will change the city for the worse. London is a walking and cycling city, not a motorway city of the south. Let’s keep it that way.

Steve Chambers is an urban planner, and the London Campaigner for the Campaign for Better Transport.