juxtaposed border control checkpoints are currently in operation. United States: The U.S. government operates border preclearance facilities at a number of ports and airports in foreign territory. They are staffed and operated by U.S. Customs and Border Protection officers. Travellers pass through the U.S. Immigration and Customs, Public Health, and Agriculture inspections before boarding their aircraft, ship, or train. This process is intended to streamline border procedures, reduce congestion at ports of entry, and facilitate travel between the preclearance location and American airports unequipped to handle international travellers. These facilities are present at the majority of major Canadian airports, as well as selected airports in Bermuda, Aruba, the Bahamas, Abu Dhabi and Ireland. Facilities located in Canada accept NEXUS cards and United States Passport cards (land/sea entry only) in lieu of passports. A preclearance facility is currently being planned at Dubai International Airport. Citizens of the Bahamas who enter United States through either of the two preclearance facilities in that country enjoy an exemption from the general requirement to hold a visa as long as they can sufficiently prove that they do not have a significant criminal record in either the Bahamas or the U.S. All Bahamians applying for admission at a port-of-entry other than the preclearance facilities located in Nassau or Freeport International airports are required to be in possession of a valid visa. Preclearance facilities are also operated at Pacific Central Station, the Port of Vancouver, and the Port of Victoria in British Columbia, and there are plans to open one at Montreal Central Station in Quebec. Informal prescreening: In some cases countries can introduce controls that function as border controls but aren't border controls legally and don't need to be performed by government agencies. Normally they are performed and organised by private companies, based on a law that they have to check that passengers don't travel into a specific country if they aren't allowed to. Such controls can take effect in one country based on the law of another country without any formalised border control prescreening agreement in force. Even if they aren't border controls function as such. The most prominent example is airlines which check passports and visas before passengers are allowed to board the aircraft. Also for some passenger boats, such checks are performed before boarding. Expedited border controls Certain countries and trade blocs establish programmes for high-frequency and/or low risk travellers to expedite border