Motorscooter

[JohnnyGus]

Are motorscooters at 50cc allowed to be ridden on motorways?

[alan30]

Motorways MUST NOT be used by pedestrians, holders of provisional car or motorcycle driving licences unless exempt, riders of motorcycles under 50cc, cyclists and horse riders. Certain slow-moving vehicles and those carrying oversized loads (except by special permission), agricultural vehicles and most invalid carriages are also prohibited.

[snapdharlich]

So it's ok then?

[ianess]

Answer is technically YES as the regulations are specific that only those under 50cc are prohibited.
Just remember that a Honda 50 or similar is usually 49cc and you'll lose any argument with the law.

[tubeway]

I am sure that in the old days when I were a lad they used to have a big sign listing all the prohibited vehicles as you entered a motorway

[JohnnyGus]

If I were to buy a scooter advertised as being 50cc, would it almost certainly really be only 49cc, meaning it could not be ridden on a motorway?

[ianess]

Exactly that, JohnnyGus.  The bike's documentation will tell you the exact size and it will most likely be 49cc.
Most vehicle engine sizes are actually slightly less than the advertised capacity, eg a 1400 Ford Escort is really 1392cc.