That's the subject of the controversy brewing in the wake of this KIRO story:

A rollover crash on I-405 near State Route 169 on Tuesday happened after a man became enraged that a couple wouldn't speed up, the couple told KIRO 7. The couple, Linda and Soren, said they were in the carpool lane of I-405 northbound, just north of SR 169, going 60 mph, but that it apparently wasn't fast enough for a man driving behind them. Linda and Soren gave us their account of the crash, but asked us not to use their last names because the man who cut them off is still out there.

In the story's comments, a battle is raging between people who believe the HOV/carpool lane is an extension of the far-left passing lane (and should thus only be used by people ready and willing to drive over the speed limit) and those who understand the HOV/carpool lane is a separate universe from the high-speed aggression of the far left lane and can be used at all speeds by anyone with two or more passengers in the car.

The certainty of the "HOV=passing lane" camp is surprising to me. So I ask you: