The last few years have been a little confusing for consumers wanting to check the fuel economy and green credentials of their potential new vehicle purchase.
Bombarded with acronyms and figures, we all struggle to understand what it all actually means.
As climate change and global warming move to the top of our agendas, car fumes, car emissions and vehicle pollution are just as important in our car buying decisions as fuel economy.
In this blog we will try to de-mystify the jargon and help explain the tests now carried out in order to categorize new cars and light commercial vehicles.
NEDC - The Old System
The NEDC or New European Driving Cycle, sometimes referred to as the MVEG cycle or Motor Vehicle Emissions Group has been in use up until now. It has been going for many years and was last updated in 1997 – twenty years ago!
It was designed to assess the emission levels of car engines and their fuel economy. The test was supposed to represent the typical usage of a car in Europe and consisted of urban, extra-urban and combined driving cycles. It focussed on measuring CO2 emissions, fuel consumption and pollutants emitted from the exhaust system. Government regulation and components such as diesel particulate filters have helped to clean up vehicle emissions. However, the NEDC system was criticized for its figures, which were felt to be unachievable in reality.
WLTP - Time For A New System
The time was right to re-visit a way of categorising vehicles to give an accurate reflection of their efficiency. As we know, climate change and other green issues are becoming much more important to consumers considering purchases not only in the motor industry, but in all aspects of daily life.
Cue the WLTP or Worldwide Harmonized Light Vehicle Test Procedure. This has been developed with input from across the European automotive industry and is now spreading across the world as an agreed standard. This is still a lab-based test but seeks to simulate modern driving styles and conditions for passenger carrying vehicles and light commercial vehicles.
For example, the WLTP is 10 minutes longer than the NEDC, its velocity profile is more dynamic, consisting in quicker accelerations followed by short brakes. The average and the maximum velocities have been increased to 46.5 km/h and 131.3 km/h respectively. The distance covered is more than double the 11 kilometres of the NEDC.
Now the impact of the model’s optional equipment is also considered. In this way the tests better reflect the emissions of individual cars, and not just the one with the standard equipment (as it was for the NEDC cycle). The procedure now needs two measures: one for the standard equipment and the other one for the fully equipped model. This takes into account the effect of the vehicle’s aerodynamics, rolling resistance and change in mass due to the additional features.
The WLTP tests have had to be carried out by all manufacturers on their complete model range between September 2017 and September 2019.
RDE - Further Measurements To Improve Accuracy
As updated lab-based tests were still felt to not reflect real world driving conditions, a complementary test is being introduced.
The Real Driving Emissions (RDE) is another round of tests being implemented across all cars from all manufacturers to measure emissions under real world driving conditions. It will be introduced on 1 September 2019 to complement the Worldwide Harmonised Light Vehicle Test Procedure (WLTP).
These tests make sure cars deliver low emissions on the road, with RDE focusing on N0x and other emissions.
Under RDE, a car is driven on public roads and under various driving and external conditions, that include different heights, temperatures, extra payload, uphill and downhill driving, slow roads and fast roads. To measure the emissions during the on-road test, vehicles are equipped with a portable emissions measurement system, or PEMS, that monitors pollutants and CO2 values in real time. This helps to verify that legislative caps for pollutants are not exceeded under real use.
As we know, the government taxes vehicles based on their emissions values, so this has been an important aspect to get right. All vehicles sold after 1st September 2019 must now be RDE compliant.
It is hoped that consumers will be able to rely on more accurate information to inform their decision to buy a new vehicle.
So, you can be sure that the figures quoted moving forward will be a truer and more accurate measure of the economy, efficiency and general ‘environmental friendliness’ of your new vehicle.