Base Access Privileges Improvement Act This bill requires the Department of Defense (DOD) to maintain access standards applicable to all military installations in the United States that include certain screening requirements. DOD must ensure the access standards include a protocol for the voluntary pre-arrival registration and screening of individuals anticipating a need for access to a military installation in the United States. Additionally, DOD must maintain guidance regarding the granting of unescorted access to military installations in the United States for specified individuals (e.g., civilian employees of DOD) and ensure the guidance is circulated to the commanders of each military installation. DOD must ensure each military installation in the United States has a designated main entrance that is manned by at least one member of the Armed Forces (or civilian employee of DOD) at all times. The location of each designated main entrance, as well as the location of any additional entrance used for commercial deliveries, must be published on a publicly accessible DOD website. Finally, DOD must periodically review the standards and guidance related to access to military installations and make updates as needed.