Both Ann Arbor and Davis County in Utah are considering rapid streetcars. That is using streetcar vehicles that can carry up to 160 people on a 66 foot long platform versus light rail vehicles which typically are about 90 feet and have a capacity of over 230. Compare that to an articulated bus which only holds about 100.
Both are discussing using exclusive lanes in the street to move much faster than traffic. The applications however are a bit different. Ann Arbor is looking to build lines on four main corridors and feed them with neighborhood shuttle buses. It's more like a city tram system.
The Davis County version is a feeder to commuter rail and would travel in its own lane except in two places. I wish I knew where those two places were but I'm guessing we'll find out eventually.