Mind the Gap 2015: Closing the chasm between test and real-world car CO₂ emissions

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.

This report definitively shows current systems for vehicle testing of fuel economy and CO₂ emissions don’t work and the proposed introduction of the new WLTP test seems likely to deliver limited and only temporary improvements. Systematic changes to the way cars are tested, regulated and taxed are needed to ensure cars are decarbonised on the road and not just in laboratories. The technologies to reduce emissions are available – what is missing is a robust policy framework to ensure these are delivered.