New diesel vehicles from three brands have exceeded Japanese emissions levels in on-road testing.
Two Toyota vehicles and a Nissan vehicle tested emitted up to 10 times the amount of nitrogen oxides, or NOx, than the required laboratory-tested standard.
The Japanese transport ministry tested six types of diesel vehicles. It found no ‘cheat’ software.
Diesel vehicles sold in Japan are currently subject to only laboratory tests for emissions, but the government is considering adding on-road testing – following moves in Europe and the US triggered by the Volkswagen emissions scandal.
France, which set up a special commission last year that would oversee the testing of 100 cars under real-world conditions, said in January that several cars tested by the commission, including one Renault model, had been found with excessively high exhaust emissions.
The vehicles with the biggest emissions gaps were certain versions of Toyota’s Hiace van and the Land Cruiser Prado sport-utility vehicle, Nissan’s X-Trail SUV and Mitsubishi’s Delica D:5.
Mazda CX-5 in street tests yielded almost the same emissions result as the laboratory test standard, while the Demio, known as the Mazda2 overseas, had only a small gap between the lab standard and the field-test result, authorities said.
Toyota “will continue to make improvements to reduce NOx emissions during on-road vehicle operation,” a company spokesman told the Wall Street Journal, with Nissan and Mitsubishi giving similar answers.
It is believed cold weather may have affected the tests, with engines potentially switching off exhaust recirculation systems as a protection measure.
Diesel sales make up just 4% of the Japanese market.
