This map shows routes from Girton (off the top left) to the Grafton Centre, in Cambridge.
(1) is my initial "naïve" route; which is probably the shortest, but one runs into too many pedestrians and traffic-lights.
(2) is my first revision, based mainly on the fact that I tend to turn down Oxford Road to get to a lot of other places, but as is clearly visible from the map (if not my head) it's much further).
(3) describes a simple optimisation to (2) that turns out to be generally helpful.
(4) was the next approach, but I quickly realised that the optimisation (5) that I used to use from Darwin Drive was still applicable.
(6) is the route I currently use, I think it's probably the most optimal, particularly since if the traffic is heavy at the turn-off point you can revert to (5).
(7) is a rejected optimisation to (2) that experimentally took longer than the original.