Comment by mmooss

> A bus only lane is also a vehicle lane that is sitting empty a good part of the time.

A rail track for the same route sits empty just as much.

> you can add additional lanes almost indefinitely, and it doesn't really help congestion that much.

I don't think adding bus-only lanes would have that effect. Adding lanes for private vehicles reduces congestion, which encourages people to move to places along the route until the congestion reaches the previous barely-tolerable level (as I understand it).