If it is such a bad law, why do so many states have it? In fact, many states say 40 (the most common) or 45 (California) feet, for a "combination of vehicles", not 30.
FMVSS (Federal Motor Vehicle Safety Standards), IIRC, say 40 feet.
ALL of them are from 20 MPH!
I am merely stating what the law IS. I can't explain WHY it is what it is, nor am I particularly concerned whether the law makes sense or not. If I can find them, I report on them, usually quoting the exact statute for reference.
Think about this: It is easy to find an unoccupied piece of pavement where a 20 MPH test can be done. Where will you find an unoccupied, level, piece or road to do a 60 MPH test to see in the vehicle can stop within 150 feet?
As always, the bottom line is: If you don't like the law, contact your state legislators to get it changed. If you can get enough people on board, maybe your person will get the law repealed or changed.
While you are at it, don't forget to contact your Federal representatives and demand that the FMVSS be changed, as well.
Good luck.