Unfortunately the RAFP have got jurisdiction over some roads off camp by arrangement with the local plods. At Leeming they can book you up to the roundabout by the A1 and at Dishforth they are using radar guns on the public road leading up to the gate. Whether or not this has been tested in court I don't know but I'm not going to be a guinea pig. (no pun intended)
PS did you know that if pigs could fly, Scotland Yard would be Londons 4th airport.