Volkswagen Scandal: how can we make our cars cleaner?

Around 11m owners of Volkswagen's diesel-engined cars this week discovered that when they drive to work, take their children to school or make a road trip they may be emitting more harmful pollutants than they were led to believe.

According to the US Environmental Protection Agency, half a million VWs in the US were fitted with “defeat devices,” designed to detect a test and stop tailpipe emissions only when the car is being tested in the laboratory, but spew it out when real drivers are on the roads. VW has since said that about 11m of its cars carry this device globally.

VW chief executive Martin Winterkorn may have stepped down yesterday, with the promise of allowing the auto giant to turn over a new leaf, but the scandal is far from over, as drivers, environmental campaigners and politicians demand to know the scale of the issue—were European cars also affected, and are other car makers pulling similar tricks?

Italy, Germany and South Korea have begun investigations, but despite growing pressure, the European Commission has so far shied away from starting one of its own, suggesting instead that such work should be the preserve of national governments.

Green campaigners have long complained that automakers were exploiting loopholes in the testing regime that allowed them to overstate the environmental benefits of their latest models. Yesterday it emerged that the German government knew about defeat devices in July this year. Even back as far as 2011, then European Environment Commissioner Janez Potonik acknowledged "some cars may be 'tweaked' to fulfil the required test cycle in laboratory conditions but run outside the optimum when they are on the road," though he was speaking in general terms, not referring to the practices of any specific manufacturer.

Four years later, we are still choking on polluted air and most of the UK's biggest cities remain decades away from meeting legal air quality limits. Analysis by the Guardian following the VW scandal estimates the company's cars may be responsible for up to 1m tonnes of previously undetected air pollution each year, which is equivalent to the UK's combined emissions for all power stations, cars, industry and farming.

The problem and the fix is in the test cycle, which renders the ever-tightening pollution rules impotent. Earlier this month, the new Euro 6 standards came into force, which aim to radically cut the nitrogen dioxide emissions from diesel cars. But the testing cycle, which was developed in the seventies and involves cars being examined on something that resembles a complicated treadmill, isn’t up to the job.

Studies by the International Council on Clean Transportation (ICCT) have shown cars which officially met the Euro 6 limit for NOx emissions in the laboratory actually exceeded the limit by up to seven times on average when measured in real-world conditions and that on-road carbon dioxide emissions are on average 38 per cent higher than lab-tested emissions.

Much of this is down to carmakers increasingly exploiting loopholes in the test procedure, such as taking out car stereos or spare wheels to lighten the load and reduce power consumption. How many automakers were also using defeat devices remains to be seen, but it is clear that the lax testing regime opened the door for some car companies to expend too much time and energy learning how to beat the system rather than deliver genuinely low emission cars.

The Commission reckons its tough new test procedure, due to start in 2017, will stop manufacturers using defeat devices and give a much clearer idea of the actual emissions a car is likely to produce. Yesterday the European Parliament’s environment committee voted that no loopholes or deviations be allowed for pollution limits in the tests in this new regime.

But even if this new test cycle delivers a step change in the performance of cars, it will already be too late for the hundreds and thousands of people suffering poor health or early deaths each year because of the toxic pollution pumped out by the cars on our roads.