Another alternative is some cameras. With enough strategically placed cameras and big fines, jumping across the line would be financially non-viable for most people. Hell, after a couple camera tickets, they could ban your plates from HOV entirely so if a cop caught you in HOV they could use the big stick.
Just to play devils advocate, weren’t you against speed camera fines in the other thread a while back? Automatic camera tickets for one thing is good whilst not for the other?