Trucks

A couple weeks ago, the state police pulled this massive sting-operation where they pulled over big-rigs.  When I first heard this, I thought the truckers were being cited for exhaust emissions.  Turns out, they were pulled over due to faulty air-brakes, though the news report failed to specify exactly what the problem was.  How do the police know there's something wrong with the air-brakes?  Those things are tested and certified at the factory, if any problem discovered later, the factory would issue a recall.  Who is a police officer to just spot a truck and pull them over because of the braking system?  Are they mechanical engineers?  How can they simply detect a problem with the brakes when a vehicle is still in motion?  The entire premise of such an operation is egregiously absurd, and it my personal opinion that those police officers should be cited for pretending to be mechanical inspectors when they are, in fact, not.  There should be a law against that.