I'm specifically thinking of Utah having specific merge zones for the carpool lane - which many many people simply ignore.

I've seen way too many near-misses due to someone flying along in the carpool lane and then having someone merge over from the passing lane unexpectedly. If we could get folks to honor the merging lanes - so that people traveling in the carpool lane knew when to be extra vigilant - I think it would make unlimited speed in that lane much safer.