Won't those be empty 99% of the time? Sounds wasteful.
Of course, at this point, you might as well use streetcars. But I think buses are still cheaper at that point.
EDIT: Nevermind, this is it: https://news.ycombinator.com/item?id=17034100
I'm just wondering if a better use of the street could be achieved; that doesn't have to mean cars. What about a bus + moped lane? Electric mopeds seem like a pretty good alternative for people who need something faster than a scooter, and having ridden a bicycle in Amsterdam, where mopeds could use the bicycle lane, I can tell you they don't belong there!
They use a trick: where the bus lane merges they have a traffic light. Cars have to wait for the bus -- literally -- and are only allowed to merge behind the bus. When the bus stops there are street baffles preventing the cars overtaking the bus. This way the bus has a free lane ahead. And the cars would have needed to wait in the traffic jam anyway, so why not let them wait intelligently behind buses?