If you plan on arriving at the airport using your own vehicle, you may use one of the following motorways or smaller national carriageways/highways, depending on your point of origin.

Principal Access Route: 
A22 Motorway (called ‘Via do Infante’),
National Highway 125 (Estrada Nacional125)

Other Access Routes (Secondary Roads):
IC-1
N2
N120
N122

Internationally:
N431 (from Huelva, Spain)
A22 Motorway (Via do Infante, Portugal)