GJudge...
Our rights of way are categorised as follows:
BYWAYS OPEN TO ALL TRAFFIC
These can be driven by any motor vehicle unless there is a legal notice at the end saying otherwise. The sign may show a car or a motorcycle with a line through it. This would indicate that the byway has been permanently restricted to traffic.
A sign tied to a post at the end of the byway may mention dates between which the lane may not be driven - such a restriction may also be present where the car or motorcycle is shown, this would represent a seasonal closure that takes place every year. foe example, a lane local to us shows a car in a red circle with a line through it, and the notice "October to March", so the lane may not be driven except from April 1st to September 30th.
RESTRICTED BYWAYS
these are completely illegal to drive. It is sometimes difficult to differentiate between these and normal byways because some councils have downgraded a number of byways to restricted byways and might not have changed the signs. The best way to check these is to go out with someone who knows... or check the difinitive map at the local council office.
BRIDLEWAYS
don't be tempted. You will sometimes see bridleways that have tracks that look as though another 4 x 4 has already driven them. That may have been a farmer or someone else who has legitimate access. Trust me it ain't worth the risk.
FOOTPATHS
These are for walkers alone. No excuses.
ORPAS (Other Routes With Public Access)
These may sometimes be roads, and sometimes will be unmetalled. By and large if they show up as roads it is OK to drive them but again the council map will give you a definitive answer (forgive the pun).