Hackney carriage
A hackney or hackney carriage (also called a cab, black cab, hack or London taxi) is a carriage or car for hire. A hackney of a more expensive or high class was called a remise. A symbol of London and Britain, the black taxi is a common sight on the streets of the UK. The hackney carriages carry a roof sign TAXI that can be illuminated to indicate their availability for passengers.
In the UK, the name hackney carriage today refers to a taxicab licensed by the Public Carriage Office, local authority (non-metropolitan district councils, unitary authorities) or the Department of the Environment depending on region of the country.
In the United States, the police department of the city of Boston has a Hackney Carriage Unit, analogous to taxicab regulators in other cities, that issues Hackney Carriage medallions to its taxi operators.