Agreed, but when you say "half", are you talking distance or time? My experience is that once you're in the tunnel, it's pretty quick. Surface streets are achingly slow.
I agree, though I'm not sure if this is a possibility with a single set of tracks.
Aside from bart or muni in the tunnel, I found the fastest public transportation in SF was the various limited or express buses that go from the richmond to downtown. They make very few stops and move quickly.
The thing is, the express buses can easily pass the slower regular bus that make every stop. That wouldn't be possible with the streetcars, which I think would have to be all or nothing.
