It's not using the google API for "shortest driving distance".
From the about page (http://ridesf.com/about
"The site backend is powered by Postgres
with the PostGIS
extension and the routing is found with the pgRouting
A small C cgi app returns the path in a variety of formats (GPX
, & JSON
The data for the bike lanes is a combined version of data from the CA MTC
and Tiger Line Data
from the US Census.
The route is displayed using the Google Maps API
It is mostly useless right now since I don't have a conflated data set that includes bike lanes and non bike lanes. It really is just a work in progress/hobby.