Matthias Mueller has been named as Volkswagen (VW) Chief Executive in the wake of the scandal of rigged emissions tests in diesel cars. He succeeds Martin Winterkorn, who resigned on Wednesday. VW, the biggest carmaker in the world, admitted cheating on emissions tests in the US. US Department of Justice (DoJ) told BBC that it would join the US Environmental Protection Agency's (EPA) investigation into Volkswagen. Some VW cars being sold in America had devices in diesel engines that could detect when they were being tested, changing the performance accordingly to improve results.