Addressing some of the above: (sorry I don't know how to quote, haven't really done forums like this for awhile).
1) I use 95 north and south every day from south of springfield to maryland. The HOV lanes have varying travel times and I often have to take a gamble as to whether or not the HOV lanes will be faster or the regular lanes. It would be nice to have waze make that decision for me. Today is a great example of the problem-there was a major accident on 95 south so I took a chance and took the HOV lane home (it was after 6 pm so they were open). Waze wanted me to take rt. 1 south instead. Route 1 has a lot of lights on it and is usually also congested so I decided against it. Luckily, my bet paid off and the HOV lanes were clear. There are two things to realize about the HOV lanes on 95 in particular:
a) Even though they are reversible, the exits to get on them are very far apart from the exits to get onto the regular 95. There are gates blocking cars from getting on the roads so if it is closed you can't physically get onto the road and go the wrong way...I've seen people try, it doesn't work. So, if waze tells you to take the HOV lanes, and the gate is closed, it will automatically reroute you because you will have to make a distinctly different turn. This is significant, because in other places where the roads are close together, waze doesn't necessarily know what road you're actually on: If waze says to take 495 thru across the woodrow wilson bridge and you take local instead, waze won't figure it out until you exit because the roads are so close together and there is not a significant turn to take one or the other.
b) HOV2/HOV3, etc. is clearly marked on the signs. It would be nice to get a warning from waze, as other gps systems are able to do, but if you drive in the area regularly you should know the law and be able to read the signs.
To point b above, I could see this being a problem with thru travelers, new residents or folks who just don't pay attention to details. That's exactly the reason I suggested making them toll roads. If a user is familiar/intelligent enough to figure out when the lanes can be used, just mark them toll roads and let the user decide if they want to take the risk. I realize there are other problems with this method, such as being routed onto a toll road unexpectedly when leaving the feature on to use it for HOV lanes. Long-term, there really should be an HOV lane designation. I don't think the differences between HOV3 vs HOV2 or HOT lanes are significant, as there are multiple signs on the road itself and the user should be able to determine if the roads can legally be used or not.
2) The speeds are significantly different on HOV lanes vs. regular at certain times of the day. This can make a big difference in travel time. To that end, the current system of having the entire road marked as a parking lot road works very well once the user has chosen to take the road (assuming waze recognizes you are on the road, which is not always the case depending on the severity of the turn onto it-see above). Once the user is on the road and waze recognizes this fact, waze can handle the resulting routing. The only problem is that the user assumes the risk of actually getting onto a slower road when he initially makes the decision to switch to the HOV lanes, as there is no estimated time on waze, he just has to assume the HOV lane will be faster. This mostly comes into play when there is an accident in the HOV lanes. On 95 and 495, this is detrimental, because of the jersey barriers-once you get into the lanes you cannot get out except at designated exits.
3) I66 inside the beltway is another beast entirely. I have no idea how this road works. My Garmin constantly wants me to take this road and I have to bail. This is one of the few roads that is also consistently monitored by police so a mistake can cost you.
4) Non-isolated HOV lanes are insignificant, such as most of I66 outside the beltway. This discussion also applies to parts of 270 north of the beltway, and likely other roads I am unaware of.
My $0.02, a little long winded. Now that the 495 HOT lanes are open they should be specifically addressed at a minimum.