West Country asthmatics breathed a deep sigh of relief last week, as Bristol city council unveiled long-awaited plans for a clean air zone in the city. The proposals would see a total daytime ban (from 7am to 3pm) on diesel vehicles entering a small central zone – a first in the UK, though increasingly common across the continent – plus a new charge for entering a wider area.

If approved tomorrow, the scheme will come into force in 2021. It cannot come too soon for Bristol’s most vulnerable residents: illegally poor air quality currently contributes to 333 annual premature deaths from respiratory illnesses in the city.

Preliminary results from a similar scheme in London, the ultra-low emission zone (ULEZ), are even better than expected, with toxic nitrogen dioxide (NO2) emissions down by nearly a third, demonstrating that this approach can really work. In one respect, Bristol’s plan goes one better, as its proposed scrappage scheme – financial compensation for ditching old diesel vehicles – includes an option, unlike London’s, to redeem value against an electric bicycle or on public transport.

But one curious feature of the plans exposes Bristol’s clean air zone as a microcosm of national policy paralysis, and demonstrates a collective failure of imagination on transport and the environment. The city intends to charge commercial diesel vehicles including buses for entering the wider clean air zone – while exempting private cars. They argue that charging private motorists would disproportionately affect low-income households that depend on their cars to get around, and in the absence of alternatives this is undoubtedly true.

But this is exactly the wrong way of thinking about the problem. A fifth of children in Bristol are in low-income families, and are far less likely to have access to a car than their better-off peers. Leaving the streets filled with dirty cars means throwing these children under the SUV. What is required is urgent action to ensure that nobody in Bristol is dependent on their cars for mobility.

This is the heart of the issue. The years of foot-dragging and buck-passing between central government and city authorities on air quality are just one aspect of a fundamental societal intransigence. At every level of government, politicians have been too blinkered and cowardly to challenge the primacy of the private car as the dominant mode of transport in Britain.

As a result, transport is now the largest sectoral source of carbon emissions in the UK. Private cars make up the bulk of these emissions, and they are still rising – even in the teeth of the escalating climate crisis. Expectations that switching to electric vehicles will be equal to the task are wildly at odds with the evidence. Estimates suggest that meeting our climate commitments under the Paris agreement will require an overall reduction in vehicle miles travelled in the UK of between 20-70% (depending on how fast we switch to EVs). But there are no measures to reduce traffic volumes in the government’s decarbonisation plans. Instead, they intend to spend more than £30bn of public money on road building to facilitate a 50% increase in traffic between now and 2050.

While rural areas and small towns are likely to remain dependent on cars for the foreseeable future, major cities such as Bristol need to treat this existential imperative as a golden opportunity to improve quality of life for residents by making private cars completely obsolete. Bristol is well placed to lead this transition. It is one of only half a dozen places in the UK where more than half of all trips are already made by walking, cycling or by public transport, and where bus journeys are actually increasing rather than declining.

Moreover, the city’s mayor, Marvin Rees, was one of the most senior Labour political leaders to sign up to the Green New Deal motion at the party conference, aiming for UK net-zero emissions by 2030. But taking this pledge seriously demands a leap of imagination far beyond anything in the city’s new clean air zone proposals.

This is much more achievable than it may initially seem. Cars were always a perversely poor solution to the basic geometry problem of moving lots of people short distances around densely populated areas. Exciting new frontiers are opening up in urban personal transportation all the time now, from shared rides and vehicles, to electric buses and rickshaws, to micromobility solutions such as dockless bike hire schemes and e-scooters. Many of these emerging solutions are not just better for society and the environment, but offer a superior user experience over private cars, daily traffic jams and the demoralising musical chairs over a parking spot.

More prosaically but just as importantly, more and more cities across Europe are realising that free public transport makes sense for them, and that citywide cycling infrastructure creates network effects that radically alter the attractiveness of cycling versus driving.

It can’t happen on its own. British society was systematically motorised through a series of investment and regulatory decisions in the 1950s and 60s, when the government forced the closure of thousands of miles of railway lines while constructing a thousand miles of new motorways. Deliberate choices by governments gave us the broken and toxic transport system we currently have, and they can give us the transport system we need to prosper in the 21st century too. But first we need the courage to imagine better, and then to demand it.

• Leo Murray is co-founder of the carbon-cutting campaign 10:10