Volkswagen installed defeat device software in their diesel vehicles that could detect emission testing scenarios. During tests the software would put the engine into a "safe mode" where it met emissions standards, but on the road the vehicles emitted nitrogen oxide at levels up to 40 times the legal limit. In 2015 Volkswagen admitted to cheating emissions tests in the US, affecting 11 million vehicles worldwide. The scandal has major financial and reputational costs for Volkswagen, and they have launched initiatives to repair damage, increase compliance, and address customer concerns regarding affected vehicles.