HOV usage rate is both city and time-dependent
Note "time dependant" is not just the rate of use; the road is only HOV for certain times during the day, as opposed to 24 hours. When the road is non-HOV anybody can use it. Typically the HOV restriction is only for 2-3 hours a day during the rush hour.
But if I am a visitor to that area on a business trip, commuting in the morning with all the locals, and am totally unfamiliar with the situation, I may decide to trust Waze in such a "mature area" and might get routed onto an HOV lane, recognize it too late and get fined.
Also a relevant point. I noted earlier that thru travelers would have a hard time making the decision that is obvious to the locals, as to whether or not to get on the HOV. The same is true for visitors. This is exactly why I don't understand the I66 setup-if you get on I66 inside the beltway as a non-HOV driver, you WILL be fined. There is a cop sitting at every exit checking cars. Driving east on 66, there is a split in the road where you can either continue on 66 (but the entirety of 66 is now HOV), or you can exit onto the beltway around the city. The beltway around the city is almost never faster, but you have to do it if you're alone in the car. Waze doesn't know this. So why is I66 left as a routing option?