Bus Conductors. Until the 1970s & early 1980s, conductors, or clippies, were a common feature of many local bus services. Two-person crews were needed because until the 1960s, all double deck vehicles were built with front-mounted engines & a "half-cab" design. 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").