Here's a longish interview with Walter Hook, director of the Institute for Transportation and Development Policy, in which he extols the virtues of "bus rapid transit" systems as being able to provide as good service as trolleys at a fraction of the cost in crowded urban areas.
Well, in most cases:
... Of course, you can mess up a BRT system, and Boston's Silver Line proved that you could waste almost as much money on BRT as you can on a rail system. ...
Via CommonWealth Unbound.