In previous threads nobody has been able to come up with a real policy on how they are supposed to handle it
http://www.flyertalk.com/forum/hertz...ou-arrive.html
for example.
I know many hotels have a very specific policy on what they can and can't do for you , I would assume some car rental agencies should too. Though that's assuming too much.
And according to a story in USA today a few years back (though in this case, when they ran out of cars, they just closed the counter, leaving those who did not arrive yet stranded)
If no cars are available at all, the location's staff should provide alternate transportation to your destination, such as a taxi ride to your hotel. The company should then deliver your vehicle as soon as possible. If that's not feasible, you can rent from a different agency, and if your new rental price is higher, the car rental company you originally booked with should reimburse you for the difference. This may require some negotiation, as technically the remuneration standard applies only to rentals of similar cars, and in a pinch, you might not have many choices.
Hertz was waiting for ....... to send in the receipt for his replacement rental so it could refund the extra cost he incurred, according to Rivera. Rather than make him wait any longer, Hertz sent ....... a $50 voucher for a future rental as a gesture of goodwill.
http://usatoday30.usatoday.com/trave...ntal-car_N.htm