You could try a Municipal Awareness Parchment.
or MAP for short. Apparently Ordnance Survey provide these scientific devices very cheaply. Available in all good bookshops.
There's a very useful thread on "how to find greenlanes". After reading it, i got my local Landranger map and in 30minutes I found two dozen potential lanes, then went out for a reccy.
Luke 10:37 "...go and do thou likewise."