Many small and mid-size airports have a single two or three-lane one-way loop road which is used by local private vehicles and buses to drop off and pick up passengers.
An international airport may have two grade-separated one-way loop roads, one for departures and one for arrivals. It may have a direct rail connection by regional rail, light rail, or subway to the downtown or central business district of the closest major city. The largest airports may have direct connections to the closest freeway. The Hong Kong International Airport has ferry piers on the airside for ferry connections to and from mainland China and Macau without passing through Hong Kong immigration controls. – Grand Limousine