A laboratory test follows standardised and repeatable procedures that allow the emissions of different models of cars to be compared to each other. There are, however, many variables affecting real-world driving emissions produced by a car on the road, which simply cannot be taken into consideration in these lab tests.
Two different people drive exactly the same car under the exact same conditions; do they have the same emissions?
No, they will each have different emissions. This is mostly due to the fact that each of the individuals will have different driving styles – one might accelerate faster, take corners faster or brake more suddenly than someone driving more cautiously.
However, as there is no single real-world emission value, only values obtained through standardised laboratory tests allow us to compare the emissions and fuel consumption of different car models from different automobile manufacturers.
The European Union has introduced a new lab test, called WLTP, which ensures that laboratory measurements better reflect the emissions and fuel performance of a car. However, although more accurate, even the new test cannot provide a perfect representation of real driving.
Despite the accuracy of the Worldwide Harmonised Light Vehicle Test Procedure, it remains impossible to reproduce during a standardised laboratory test all the conditions that can be encountered in real world driving by each driver.
So, even though the new lab test is much more accurate than the old NEDC test, there will still be a difference between the CO2 emissions measured in the lab and the real world.
WLTP simply cannot cover all variations globally – and certainly not every individual driving style. Also in the future, driving behaviour, traffic and weather conditions will continue to differ from one country to another – and therefore individual fuel consumption and CO2 emissions will also vary.