Here is a simply and mildly practical problem.
Suppose, HoV lane is moving freely. (Supposition needed along with prayer.)
So, your idea is that you could let a small number of lucky vehicles into the HoV lane, and still not overcrowd HoV, while at the same time alleviating some congestion from the main lanes. How do you do it? Keep in mind, you can’t say every “3rd” car, since every car is a 3rd car depending upon who is doing the counting. So, your method must be deterministic based on the car. Secondly, you should be able to change your method next time this lucky scenario happens. Thirdly, it would be nice if there was a way to easily confirm the criteria from a distance.