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 tests.

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THE DIFFERENCE BETWEEN THE REAL WORLD AND A LAB ENVIRONMENT – IMAGINE THIS …learn more

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 the other who might drive more cautiously.

However, as there is no single real-world emission value, only values obtained in standardised laboratory tests allow us to compare the emissions and fuel consumption of different car models from different car manufacturers.

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WHY ARE TODAY’S TESTS OUTDATED?learn more

Driving conditions and new technologies have evolved substantially since the 1980s.

  • There is an increasing availability of new technologies in today’s cars that have a strong effect on fuel consumption, for instance 4-wheel drive and a wide range of customer comfort systems (such as air-conditioning, rear window heater or heated seats and other electrical devices). These features are not accounted for using the NEDC test procedure, because they simply were not common when the test was designed.
  • Driving styles have also changed over the years, with increased traffic congestion and inefficient driving. In some countries, new car sales are led by the sale of company cars whose drivers may also receive a fuel card and may not consider fuel economy as their highest priority. Consequently, emission values obtained with the current laboratory test (NEDC) differ greatly from the emissions produced by cars on the road.

However, this does not mean that no progress has been made in reducing real world emissions, which have concretely decreased both for CO2 and for pollutants.

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MORE ACCURATE NEW TESTS WILL BE INTRODUCED, SO WHY WILL A DISCREPANCY REMAIN BETWEEN LABORATORY AND ON-THE-ROAD EMISSIONS?learn more

The European Union is finalising a new lab test, called WLTP, which will ensure laboratory measurements better reflect emission performance. However, although more accurate, even the new tests will not be a perfect representation of real driving.

Despite the accuracy of the WLTP, it remains impossible to reproduce in 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 will be much more accurate, there will still be a difference between emissions measured in the lab tests and the real world.

The WLTP 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 consumption will also vary.

WHY HAS THE DISCREPANCY BETWEEN LAB TESTS AND ON-THE-ROAD PERFORMANCE GROWN?learn more

The discrepancy between the fuel economy figures obtained using the regulatory test and what customers can achieve in real driving conditions has grown due to a number of factors, including technological advancements and changes in driving conditions.

  • There is an increasing availability of new technologies in today’s cars that have a strong effect on fuel consumption, for instance 4-wheel drive and a wide range of customer comfort systems (such as air-conditioning, rear window heater or heated seats and other electrical devices). These features are not accounted for using the NEDC test procedure, because they simply were not common when the test was designed.
  • Driving styles have also changed over the years, with increased traffic congestion and inefficient driving. In some countries, new car sales are led by the sale of company cars whose drivers may also receive a fuel card and may not consider fuel economy as their highest priority.

DOES THIS MEAN THAT CARS ARE NOT COMPLYING WITH CURRENT LEGISLATION?learn more

No, manufacturers are complying with the existing legislation as agreed by the European Parliament and the national governments. While the existing legislation may refer to ‘normal driving conditions’, as yet there is no protocol or testing method specified other than the current test cycle (NEDC). Compliance of pollutant emissions is therefore verified with NEDC.

Manufacturers comply under NEDC, but it is known that NEDC results do not accurately reflect conditions on the road. The new test cycle (WLTP) will be a better representation of today’s real-world driving conditions. Moreover, the new test will be complemented by the ‘Real Driving Emissions’ (RDE) test to ensure that vehicles deliver low pollutant emissions, not only in the laboratory but also on the road.

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It remains impossible to reproduce in a standardised laboratory test all the conditions that can be encountered in real world driving by each driver. So even though the future lab test will be much more accurate, there will still be a difference between emissions measured in the lab tests and the real world.

The WLTP 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 consumption will also vary.

Read More