EU regulators will draft legislations that will require vehicle fuel use to be tested on roads instead of in laboratories in an attempt to close loopholes that allows car makers to exaggerate fuel saving and emissions credentials.

Tougher EU testing standards will be enforced starting on Sept. 1, in line with a worldwide push for accuracy, according to Reuters.

More-strict standards are likely to be opposed by most automakers.

A report conducted by the European Commission issued in 2013 revealed that lab techniques, like taping up car doors and windows, or driving on an unrealistically smooth surfaces, were the reasons behind approximately a third of a recorded drop in average EU emissions of planet-warming carbon dioxide (CO2), linked to reduced fuel consumption, according to Reuters.

An EU official confirmed to Reuters, speaking under anonymity, that "a new real-world testing method" was expected before the end of 2014.

"In the real world we have seen that NOX emissions are higher than indicated by the test, up to a factor 4 or 5 and exceptionally more," one EU official said.

The Commission says nitrogen oxide (NOX) emissions, which is linked to lung disease and hundreds of thousands of early deaths, have been miscalculated to a greater extent than CO2 levels.

Under the testing regime from Sept. 1, diesel vehicles should emit no more than 0.08 gram (80 milligrams) of NOX per kilometer.

The Commission, along with environmental groups from around the world, believe that even in the new regime, loopholes mean such emissions will be higher.

The old tests are based on a 0.180 g/km limit as part of a reduction from 0.5 g/km over 15 years.

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