The Access Pass admits the pass owner and up to 3 adults in the same car (children under 16 are always free). Access Passes can be obtained in person or via mail ($10 processing through mail) and may also provide a 50% discount on some amenity fees charged for facilities and service such as camping, swimming, boat launching, etc.
The Forest Service, Fish and Wildlife Service, Bureau of Land Management, USACE, and Bureau of Reclamation all also honor the Access Pass at sites where entrance or day use fees are charged.
For more information or to download an application visit the National Parks Service website: https://www.nps.gov/planyourvisit/passes.htm