Divergence between real-world and manufacturers’ type-approval CO2 emissions for various real-world data sources, including average estimates for private cars, company cars, and all data sources. Source: The ICCT. Click to enlarge.

This update, jointly prepared by the ICCT and the Netherlands’ Organization for Applied Scientific Research (TNO), describes the increasing real-world efficiency gap using statistical analysis.

We analyzed data for more than 1.1 million vehicles from eight European countries, and all data sources confirm that the gap between sales-brochure figures and the real world has reached another all-time high. When we published our first study in 2013, the gap had widened over ten years from roughly 10 percent to around 25 percent. Now it has increased to 39 percent for private cars, and 45 percent for company cars.

—Uwe Tietge, a researcher at ICCT Europe and lead author

The latest ICCT analysis did find a slowdown in the rate of increase in the gap, in particular for company cars. However, said Tietge, it is too early to tell whether the gap will flatten off.

The analysis draws on data from 14 different sources: the user websites spritmonitor.de (Germany); HonestJohn.co.uk (United Kingdom); Fiches-Auto.fr (France); the fleet management and fuel card companies Travelcard (Netherlands); LeasePlan (Germany); Allstar fuel card (United Kingdom); and Cleaner Car Contracts (Belgium and Netherlands); the car and consumer magazines AUTO BILD (Germany); auto motor sport (Germany and Sweden); the vehicle testing organization Emissions Analytics (United Kingdom); the car website km77.com (Spain); and the car club TCS (Switzerland).

Manufacturers measure vehicle fuel consumption in a controlled laboratory environment. Since September 2017, a new test procedure, the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), has to be followed for new vehicle types. From September 2018 onwards it will become mandatory for all new vehicles.

The ICCT researchers expect that because the WLTP more accurately reflects real-driving conditions it will help cut the real-world gap approximately in half.

But even the new test procedure contains new loopholes that could permit the performance gap to increase again in the future. Further actions are therefore required, in particular on-road testing of fuel consumption and CO₂ emissions under real driving conditions and a not-to-exceed limit for the real-world gap, as it already exists for air pollutant emissions today.

—Peter Mock

The United States demonstrates how a comprehensive set of policy measures can help to contain the real-world gap.

Divergence between real-world and manufacturers’ type-approval CO2 emission values for China, Europe, Japan, and the United States. Source: The ICCT. Click to enlarge.

In the US, independent surveillance testing of actual vehicles on the road has been standard practice for many years. It is no surprise that the increase in the real-world gap has been much lower in the US than in Europe. In fact, the fuel consumption values communicated to consumers in the US paint a very accurate picture of the average real-world fuel consumption.

—Uwe Tietge

On 8 November, the EU Commissioner for Climate Action and Energy, Miguel Arias Cañete, is expected to announce a regulatory proposal for reducing CO₂ emissions of new cars and vans for the 2020–2030 time period. It remains uncertain whether the Commission’s regulatory proposal will also include policy instruments to tackle the discrepancy between official and real-world CO₂ emission levels.

• From laboratory to road: A 2017 update of official and “real-world” fuel consumption and CO₂ values for passenger cars in Europe

• From laboratory to road international: A comparison of official and real-world fuel consumption and CO₂ values for passenger cars in Europe, the United States, China, and Japan