Originally Posted by
drzoidberg
I don't think you can. The additional driver, for liability reasons, has to be added before picking up the car at that location.
Correct. You need to close out the original reservation and start a new to add a driver. However, "The following individuals, if 25 years of age or older and in possession of a valid driver's license, may drive the car with the renter's prior permission and are exempt from Additional Driver fees:
- Renter's employer (while on company business);
- Renter's fellow employee (while on company business
- Renter's spouse or life partner.
- Disabled renters who have completed the non-licensed renter form"
This can be found at: Avis.com->Customer Service->FAQ->USA->Reservations->Rental Policies/Terms & Conditions (they don't offer a direct link to it)