All Diesels Flunk U.K. Real-World Emission Test

All 37 diesel models tested under real-world driving conditions by the U.K.’s transport ministry exceeded laboratory-based government emission limits for nitrogen oxides.

The vehicles exceeded official limits by between three and 10 times, according to the ministry. It says only Volkswagen models were rigged to manipulate the lab tests themselves. The report also notes that its relatively small test sample provides only a snapshot of the widely recognized gap between regulatory tests and on-the-road emissions.

Europe’s official limits on NOx emissions, which have been linked to smog formation and respiratory problem, have tightened 85% from 2000 to 2014. Actual on-road emissions have declined about 40% over the same period, according to the report. It notes that real-world emission tests will be added in 2017 to supplement regulatory test procedures.

The ministry emphasizes that none of the 20 carmakers it checked (aside from VW) had deliberately attempted to circumvent regulatory limits. Its test sample represents more than half the diesel passenger cars currently in use in the U.S.

The test fleet included 18 older cars equipped to meet Euro 5 NOx standards, which cap NOx emissions at 180 milligrams per kilometer, and 19 newer models built to conform to Euro 6 limits, which allow only 80 mg/km. The evaluations were conducted in various locations and under different ambient temperatures and road conditions, making it impossible to directly compare results among the test vehicles.