I'm new here, so this has probably been done before, but I haven't sussed out how to find any relevant previous discussion using the search. So sorry if this is repetition.
There are lots of farm roads around Cambridge, some of which have locked gates and "bicycles by written permission only" notices, others are signed as permissive routes, others have no signs but in practice nobody actually shouts at you as you cycle through what turns out to be a farmyard.
Are there any resources that enable us to work out in advance, before discovering the sign and the locked gate, which of these roads are passable by bike, with possibly a rather long route home if the answer is "no"?
Just as an example, how about Battle Gate Road?