The term "road" is defined at section 142 of the Road Traffic Regulation Act 1984 as any length of highway or other road to which the public has access and includes bridges over which a road passes. The Concise Oxford Dictionary defines `road' as a line of communication for use of foot passengers and vehicles; while in Oxford -v- Austin  RTR 416 it was said to be a definable right of way between two points.
The expression "on a road or other public place" is employed frequently in Road Traffic legislation, for example, in the drafting of moving traffic offences at sections 1-6 RTA. A public place is a place to which the public, or part thereof, have access.
The onus is on the prosecution to establish that a particular location was a "road" or "other public place".