A park where vehicles are not forbidden also might not have any highways. Vehicles are defined in terms of being capable of transport on highways, but there are vehicles used off highways.
Just because the definition of vehicles refers to highways doesn't mean the definition is not relevant in a situation in which there are no highways.
> highway "includes every road, street, lane or right of way designed or intended for or used by the general public for the passage of vehicles"
By definition, a park where vehicles are forbidden is not a highway. Please don't act smarter than you are.
A park where vehicles are not forbidden also might not have any highways. Vehicles are defined in terms of being capable of transport on highways, but there are vehicles used off highways.
Just because the definition of vehicles refers to highways doesn't mean the definition is not relevant in a situation in which there are no highways.