Additional Driver
An additional driver is anyone besides the main renter who you want to be allowed to drive. To be covered, they must be added to the rental agreement, show their own licence and meet the same age and experience rules as the primary driver.
There is usually a small daily fee per extra driver, though some rates include one for free. It is money well spent on a long road trip, where sharing the wheel keeps everyone fresher and safer.
The important part is the insurance link. If someone who is not on the contract drives the car and has an accident, the waivers and protection can be void, leaving you liable for the full cost. Adding the driver is what keeps the cover valid.
Bring every intended driver and their licence to the counter at pickup. Adding someone properly takes a minute; discovering they were never covered after a crash is far more expensive.
Related terms
Authorized Driver
Anyone named on the rental agreement and therefore legally and insurance-wise allowed to drive the car.
Principal Driver
The main person on the booking, in whose name the contract, payment card and deposit usually sit.
Minimum Driving Age
The youngest age at which a company will rent you a car at all — often 21, sometimes higher for bigger vehicles.