It works.
If it worked, they're would be little death and serious injury (because drivers would be obeying appropriate speed limits).
But id prefer proper enforcement against those that don't obey 30 etc.
I agree.
Good chance it's those that object to 20 the most too
Exact opposite, I'd bet: those that object to 20s are most likely those that see themselves as ultimately abiding by them (hence their objection).