Are mopeds allowed on duel carriageways?????
Quick answer is no. There is a cc limitation as well as a minimum speed. Any one who takes a small cc bike on the motorway wants their head examined. Can you imagine what the affects on the bike and rider would be when an artic passes you or there is a strong side wind + the effects of a large coach/lorry, gives me the creeps just thinking about it. Having ridden on the motorways on a 250cc Yamaha years ago unless you can keep up to within 10 to 20 mph of the traffic its just not a safe ride. I suggest either a bigger bike or find a route that avoids the motorways and to a certain extent dual carriageways. If she must ride on duel carriageways then occupy the middle of the lane she is in to prevent anyone creeping up the side of you (I know from experience). Safe riding & Happy New Year.