Google Bike Routes - What Are Their Criteria?

I would love to know what criteria Google uses for making it's bike routes. They are very beta. I wanted to go from Portola Valley to San Mateo Town Hall and it sent me along El Camino - busy and with many strip malls where traffic comes and goes. Alameda de las Pulgas is a much better route with bike lane - albeit hillier.

Then I tried another route from Portola Valley to Belmont. It sent me across El Camino on to Old County Road, a road with no bike lane. It didn't think of using Brittan Avenue that has a bike lane.

Maybe Google is looking for the flattest route, or routes where I can buy things on the way:).

Does anyone else have a problem with using Google Maps for Directions using a bike.

Another annoying feature is often what you would like to do is ride on a bike to a transit point then maybe put your bike on a bus or train - it would be really good if it could combine modes of transport.