A challenge for the cartographically minded among my readers:

What's the most efficient route for visiting all Oxford's colleges?

Method of transport: bicycle. No other restrictions except that you must pass the lodge of each college. Doubling back on yourself is allowed (despite the title of the post!).

A reminder of the location of all the Colleges can be seen on this hopefully accurate map from the University website.

ETA:

I do realise this is a hard problem (Owen says it may even be an NP-hard problem) but thought it might've been the sort of thing that you clever people had already done... like the "visit all the underground stations in a day" challenge, kind of thing...