What kind of motorcycles are allowed on motorways/freeways?
What engine size motorbike is allowed on motorways/freeways?
What is the lower limit for engine size on motorbikes for using motorways/freeways?
「高速道路」＝ motorway (イギリスの言い方）かfreeway（アメリカの言い方）
「何CCから高速乗れる?」＝ What kind of motorcycles are allowed on motorways/freeways?
他の言い方も使えます：
What engine size motorbike is allowed on motorways/freeways?
What is the lower limit for engine size on motorbikes for using motorways/freeways?
イギリス 
