In Japan, they are mandatory it seems, signs that easily identify drivers that are most likely to ruin your day. Now that is a good idea I'd like to see here in the USA. Of course I'd like a NATIONAL drivers license, and national test too, and national pollution tests for all engine powered objects built since 1975. This concept of mine doesn't have a visual BS test that keeps you from upgrading the engine and exhaust system, like the typical smog tests here in the states, it would be nothing other than a pollution test for what exits the engine. CO2, CO, SO2, and the rest of the bad stuff.
Sound? Yeah, that too. Really, if it's too loud, that's not cool. I'm comfortable with loud exhaust, but not open headers on public roads.
Just learned about the Japanese drivers signs via
http://japanesenostalgiccar.com/blog/2008/03/17/happy-st-patricks-day-from-jnc/
