If you peel back the layers the only reason a difference exists is purely regulatory.
What is and is not a motor vehicle is established by the feds. In the case of golf carts the Department of Transportation established the 19.9 mph maximum speed limit and the safety equipment requirements for the carts that exceed 19.9.
If not for this some carts would have more safety equipment at 19.9 mph simply because it would fulfill a safety conscious consumer's needs. With this standard manufacturers can simply revert back to "This vehicle meets all standards for a 19.9 mph vehicle".
|