The US EPA or Environmental Protection Agency, recently called Volkswagen's bluff that it was adhering to emission controls set for its diesel engines. In its admission, the German car maker confirm that its cars were equipped with a software that enabled them to detect when they were being tested for their emissions and improved its performance to pass the test. Once the test was completed, the car returned to its higher emissions, which includes the dangerous nitric oxide, capable of causes respiratory distress. It is not just the Volkswagen cars but also the Audi and Skoda cars that are capable of cheating at emission tests.