Any size can be registered, there are several 2" ones on the road though a bit daunting as not easily seen in trafic. Most run a flashing beacon on the back of the riding trolly. Plenty of larger scales are road registered and the "pub run" is a common feature of most model traction engine gatherings.
Club inspector is fine but you may need to go to a specialist such as Walker Midgley for insurance.
Have a look on Traction Talk Forum in the miniatures section, plenty in there if you search for "registering" or "registration"
J
Edited By JasonB on 01/12/2015 18:32:44