"Executive Summary
This report [Mind the Gap] provides new evidence and understanding on why there is a growing gap
between the official fuel consumption and CO2 emissions of new passenger cars and vans
and that which is achieved by the same vehicles on the road. It demonstrates that the
current (NEDC) test is outdated and unrepresentative of real-world driving and current
vehicles, and that lax testing procedures are allowing carmakers to manipulate the official
tests to produce unrealistically low results. The report also shows that the current
supervision of testing and checks on production vehicles (to ensure these are equivalent to
tested vehicles) are inconsistent and inadequate, with manufacturers paying the
organisations undertaking and certifying the tests. The conclusion is that the current system
for measuring car and van fuel economy and CO2 emissions is not fit for purpose and is in
need to urgent updating.
Why representative, robust fuel economy and CO2 emissions data from vehicles are
essential
Providing reliable information about the fuel economy of cars helps drivers choose models
with lower running costs. Having accurate tests of vehicle carbon dioxide (CO2) emissions is
essential to enable governments to levy the correct level of vehicle taxes and ensure
regulations to reduce emissions from new cars are effective.
All drivers know that it is usually impossible to achieve the official manufacturer fuel
efficiency figures, and for some individual models the real-world emissions are now 50%
higher than the test results. The gap between official test results and typical real-world
driving performance is also growing. In Germany, the gap has increased from 7% on
average in 2001 to 23% in 2011 and consequently only half the anticipated improvement in
fuel economy (of 1 l/ 100km) has been achieved on the road. For drivers, this is adding
around €2,000 to the fuel costs of the vehicle over its lifetime. Data from Germany is
supported by other studies from the Netherlands and Switzerland. The growing gap is
leading drivers to become increasingly distrustful of official data on fuel economy, making
them less likely to consider buying a more fuel efficient vehicle.
Three reasons why the gap is growing
There is no evidence that the growing gap is caused by changes in the way cars are used
and driven. Instead, the evidence shows three principal causes:
1. The current test is unrepresentative of real-world cars and driving. Much of the
technology introduced to improve efficiency of cars is far more effective in the test than on
the road. For example, technology to switch off the engine when the vehicle is stationary is
very effective during the test when the vehicle is stationary for 20% of the cycle.
2. Cars are also increasingly fitted with energy-guzzling accessories like airconditioning,
navigation and media systems, heated-seats, etc. This equipment is not
switched on during the test and by omitting the energy consumed, the official test results are
lowered.
3. The current (NEDC) test procedures to measure CO2 and fuel consumption are
outdated and lax and contain many loopholes that carmakers are increasingly exploiting to
lower the results.
Mind the Gap! | Page 6
How carmakers manipulate test procedures
A substantial body of evidence, including a new expert study for the European Commission,
shows the many ways carmakers are able to manipulate test results. By creative
interpretation of the test procedures carmakers are able to achieve multiple small
improvements that lower the test results as illustrated in the Figure.
The test comes in two main parts - a road load test and a laboratory test - and the results of
both can be manipulated. During the road load part of the test, the air and rolling resistance
of the car is measured and the results used during the subsequent laboratory test. In the
laboratory test the car is driven on a rolling road through a test cycle comprising a series of
accelerations, steady state driving and decelerations. Fuel economy and CO2 emissions are
measured throughout the test. The results of the road load test are used to set the
resistance of the rolling road (how difficult it is for the car wheels to turn the rollers).
- The road load test
When the road load test procedures were drafted 30 years ago, no-one expected carmakers
to adjust the brakes, pump up the tyres, and tape up all the cracks around the doors and
windows to reduce the air and rolling resistance. These practices are now commonplace,
with testing facilities being paid to optimise the results of the tests. There is no evidence that
carmakers are breaking any formal rules - but they don’t need to - the current test
procedures are so lax there is ample opportunity to massage the test results.
Testing undertaken by an independent laboratory has found that for older vehicles, road load
results in realistic tests – e.g. using regular production vehicles - were on average 19%
higher than the results obtained in official tests. For more modern vehicles the average
difference was 37%, supporting other evidence that the manipulation of the road load part of
the test is increasing. These differences would result in around a 12% reduction in measured
fuel economy.
In the US, Hyundai-Kia were found to have not conducted the road load test fairly. Several
manufacturers in Europe have been successfully challenged over unfair advertisements
using official test results.
- In the laboratory
Results are also being polished up in laboratory tests by, for example, allowing the battery to
discharge during the test; minimizing the weight of the car; using special lubricants that are
not supplied with the production vehicle and testing in unrealistically hot temperatures. Once
the results have been compiled the current procedure also inexplicably allows the CO2
results declared by the manufacturer to be up to 4% below the measured results.
Independent laboratory tests, using the official drive cycle but with regular production
vehicles and without using all the loopholes in the rules, show on average 12% higher fuel
consumption and CO2 emissions than official figures reported by the carmaker. In total, the
independently executed tests lead to 19-28% (average 23%) higher CO2 emissions and fuel
consumption than the official figures reported by carmakers. About half of this is explained
by differences accruing from the road load testing, the other half comes from differences in
the laboratory testing. This is the same level as the average gap between official test figures
and real-world fuel consumption observed in Germany.
Mind the Gap! | Page 7
How much are falling official CO2 emissions the result of manipulating tests?
The extent to which manipulation of the tests has contributed to the improvement in official
CO2 figures has been estimated by consultants for the European Commission. They
conclude around 30% of the net CO2 emission reduction between 2002 and 2010 does not
result from technology deployment and that “utilisation of flexibilities may account for two fifths
to one half of the net CO2 emission reduction between 2002 and 2010.” From their
detailed findings, the causes of the current gap can be estimated to be:
• About 25% due to flexibilities in the laboratory test
• 25% – 35% due to flexibilities in the road load test
• 10-20% due to omissions from the test (like air conditioning systems)
• 10-20% due to the NEDC cycle being unrepresentative
• 10-20% from unknown causes."
http://www.transportenvironment.org/sites/te/files/publications/Real%20World%20Fuel%20Consumption%20v15_final.pdf
