Transport & Environment:

The system of testing cars to measure fuel economy and CO2 emissions is utterly discredited. The gap between test results and real-world performance has become a chasm, increasing from 8% in 2001 to 31% in 2012 and 40% in 2014.1 Without action this gap will grow to nearly 50% by 2020. On average, only one- third of the improvement in emissions claimed in tests has been delivered on the road since regulations were introduced in 2008. The claims of the car industry that they are making a disproportionate effort to reduce emissions compared to other sectors is fiction. Since 2012 the average emissions of new cars driven on the road have increased marginally.
Carmakers, not drivers, are the cause of the problem as obsolete official test results are being manipulated. Exploiting testing loopholes accounted for a gap of just 5 percentage points between test results and real-world performance in 2002. This grew to 15 points in 2010; and 24 points in 2014. Technology that reduces emissions more in the test than on the road contributes about 3 percentage points to the gap; the failure to switch on auxiliary equipment during tests added around 8 points.
Mercedes cars have the biggest average gap between test and real-world performance, with real-world fuel consumption exceeding test results by nearly half. None of the improvement in emissions measured in tests of Opel/Vauxhall cars since 2008 has delivered improvement on the road, and their real-world fuel economy is actually getting worse. Just a fifth of the apparent improvement in emissions from the launch of the Mark 7 VW Golf (Europe’s best-selling car) have been achieved on the road.


via Steve Crandall.