No person transported by the owner or operator of a motor vehicle as his guest without payment for such transportation shall have a cause for damages against such owner or operator for injuries, death or loss, in case of accident, unless such accident shall have been intentional on the part of the said owner or operator or caused by his intoxication or gross negligence.
The provisions of this section shall not relieve a public carrier or any owner or operator of a motor vehicle while the same is being demonstrated to a prospective purchaser of responsibility for injuries sustained by a passenger being transported by such public carrier or by such owner or operator.