Many States already have mandatory tests that must be passed for registration. California, for example, has a Smog test that requires a vehicle to pass a yearly emissions test. If you fail, you don't get to register until you've fixed the problem. Various other States have similar laws in place. Honestly, I wish all States had mandatory checks, the State I'm currently in does not require any vehicle to pass any checks in order to register. There's nothing like sitting behind a car that burns more oil than gasoline and getting a face full of smoke when they hit the gas. There are multiple benefits to implementing yearly checks on vehicles. It forces people to keep their cars in good running order which helps save fuel and the environment, and it gets those cars which are beyond help off the road with the added benefit of keeping new cars coming off the assembly lines to keep a supply of "road-worthy" cars on the road.