After criticism of its lab testing regimen and the use of cheating software and fuel consumption over - estimations , the US Environmental Protection agency ( EPA ) will conduct on - road testing testing to all competing 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 agencies 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 .
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.