Saw this interesting article mentioned on the Classic Rendezvous Google Group:

http://www.atlasobscura.com/articles/britain-forgotten-1930s-bike-n...

In the years that followed the construction of the cycleways, though, cars became the predominant form of transportation, and the bike lanes fell out of use. Even the Ministry of Transport forgot that it had built them. 

Thought folks here might find it interesting. Would be very cool if all major arterial highways had been constructed with accompanying cycleways.