Google has released bicycling directions for their maps:
A quick look at their map shows a thin web of connections even for a city that claims to be bike friendly
What’s really missing is topology. Notice the weirdly isolated green lines at the intersection of California and Stockton in the upper left corner…it’s on a big hill, as you can see in the topographical map.
Google could integrate vertical distance as part of the calculation for optimal path. That would be innovative.
The SF bike coalition already provides an overlay of the Google data online, but they do not calculate the climb and descent.
All this combined with crime data, as I mentioned earlier, would make for an excellent bicycle map. You could have bike paths rated by elevation using theft, robbery, assault and actual topography.