Japanese authorities said they found on-road emissions were much higher than in laboratory tests of certain diesel-powered vehicles made by Toyota Motor Corp., Nissan Motor Co. and Mitsubishi Motors Corp. sold in Japan. Two Toyota vehicles and a Nissan vehicle tested on roads emitted up to 10 times the amount of nitrogen oxides, or NOx, than the standard they needed to meet in laboratory tests, while a Mitsubishi vehicle emitted up to five times the amount of NOx it needed to meet in a laboratory test, Japan’s transport ministry said in documents released earlier this week. The Japanese transport ministry tested six types of diesel vehicles. No illegal software was found in any of the tested cars and the auto makers haven’t violated any regulations, officials said. Diesel vehicles sold in Japan are currently subject to only laboratory tests for emissions, but the government is considering adding on-road testing. […]