In Delaware we have DELDOT inspection lanes in each of the three counties. They check all the lights to see if they work, windows up/down and directional signals. Then the windshield wipers. They also have a brake test (quick stop) to see if a wheel grabs.
The bugger is the EXHAUST test! They shove a sensor up the tailpipe and read the emissions at two RPMS: 2500 and idle. My 85 280SL (euro) failed the idle today and I am on a mission to fix it.