EPA to conduct on-road testing for emission compliance
After criticism of its lab testing regimen and the exposition of cheating software and fuel consumption over-estimations, the US Environmental Protection Agency (EPA) will conduct on-road emissions testing to all diesel model vehicles. In order to make cheating harder, the agency will not disclose specific testing conditions, but regulators believe on-road testing can be imprecise and therefore the aim is to validate laboratory results. European regulators are also planning on-road testing to ensure more accurate correlation between test results and real-world fuel economy, with mandatory on-road testing in 2017. 

In the wake of the Volkswagen diesel emissions scandal, the U.S. Environmental Protection Agency (EPA) will expand on-road emissions testing to all diesel vehicles.

The agency currently conducts only a handful of on-road tests of new vehicles each year, to confirm laboratory results.

But Volkswagen's cheating and recent fuel-economy over-estimations by Ford, Hyundai, and Kia have led to criticism about the laboratory testing regimen.

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The need to find out if other manufacturers have installed "defeat device" software that allows cars to cheat laboratory tests has galvanized the EPA to expand on-road testing, reports The New York Times.

The first tests included diesels from other Volkswagen Group brands, and found that about 10,000 VW, Audi, and Porsche vehicles using a 3.0-liter diesel V-6 also had illegal software.

Volkswagen has denied the EPA's assertion that these vehicles are non-compliant.

2014 Audi A7 TDI

The agency will not disclose the specific testing conditions to carmakers, which in theory should make cheating harder.

ALSO SEE: VW In Germany Denies EPA V-6 Diesel Charges, Porsche Pulls Cars Off Sale: UPDATED

Regulators still reportedly believe that road tests are still too imprecise to completely replace laboratory testing.

Instead, the aim is to validate laboratory results, which are recorded by strapping a car to a dynamometer and running it under highly-controlled conditions.

Lab tests are conducted by the carmakers in compliance with EPA standards.

2015 Volkswagen Golf TDI

European regulators also plan to add on-road testing, although for somewhat different purposes than their U.S. counterparts.

MORE: European Makers: NOx Limits Must Rise For Real-World Emissions Tests

While the EPA is primarily looking to expose cheaters, the European Union wants to close the widening gap between its tests results and real-world fuel economy.

However, when on-road testing becomes mandatory in 2017, carmakers will be allowed to emit more than twice the current European limits for nitrogen oxides, with stricter requirements coming into effect in 2021.

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