There is a reason why I have not been using Google Maps directions for bike routes, heh-heh. Sure got into a mess with this!
Update – this came about because I was editing the reccomended route that Google Maps had provided. It is actually excellent to use with car routes but trying to adjust it for the intricasies of a cycling oute is silly. I got into more and more trouble and became all tangled up! For cycling routes, just use bikely.
Otterman speaks... 
it also doesnt allow you to go the wrong way up one way streets, or cut across private car parks or business estates, or go up alleyways etc.