Bus conductors (also referred to as conductors, or clippies) were a common feature of many bus services across Europe until the late 1970s and early 1980s. The main reason two-person crews were needed was that most towns and cities used double-decker buses for urban services. Until the 1960s, all double deck vehicles were built with front-mounted engines and a "half-cab" design, such as the familiar AEC Routemaster London bus. This layout totally separated the driver from the passenger saloons. The conductor communicated with the driver using a series of bell codes, such as two bells to start (the well-known "ding-ding"). Many half-cab double-deckers were boarded from an open platform at the rear, while others were equipped with a forward entrance and staircase and driver-operated doors. Each case required a conductor to collect fares and, especially on the rear-entrance design, supervise passenger loading and unloading. Some bus services in the late 1960s and early 1970s experimented with later-model forward entrance half-cab double-deckers—removing the conductor and having the driver sell tickets, as on the rear entrance buses that were common by that time. The hope was to have the benefits of one-person operation without the cost of replacing vehicles that still remaining service life. This idea was soon scrapped and the buses reverted to conventional conductor operation. Demise In the late-1950s, new double-decker bus designs appeared that provided higher capacity, with the engine compartment at the rear and the entrance door by the driver. From July 1966, UK transport regulations were changed to allow operation of urban double-deck buses by the driver only, who could now collect fares and supervise all passenger loading and unloading. Some municipal operators adopted rear-engine bus designs and "one-person operation" quickly, others more slowly. More conservative municipal operators continued to order new half-cab buses through the 1960s, but this type of vehicle ceased production in the UK by about 1970. This was accelerated by a UK Government grant that supported the purchase of "one person operated" vehicles, but was not available for purchase of traditional half-cab buses. Through the 1970s, the proportion of urban bus routes operated with conductors declined, as older vehicles were steadily replaced with new buses equipped for one-person operation, and operators grappled with staff shortages, rapidly increasing costs and falling usage. Hull Corporation Transport, an early pioneer in one-man-operation, became the first municipal bus company in Britain to phase out conductors in 1972.