In Ontario on some of our freeways we have what are called "HOV lanes" high occupancy vehicle lanes, which require vehicles to have multiple people in them to use. The idea is to encourage carpooling or at least reward carpooling. As you can see from the picture during rush hour the lanes carry much less traffic.

Now sure this has benefits and I take advantage of them when I can but wouldn't just widening the highway an extra lane help everybody?
Do they do something similar with highway lanes where you're from? Thoughts on it?