Introduced in 1948, the Crossley DD42/7 is a 7ft 6in wide double-deck chassis with 16ft 71/2in wheelbase. The engine used is a Crossley direct injection 6-cylinder oil engine of 8.6 litres capacity.
Three alternative transmission systems were offered, these being a 4-speed constant mesh gearbox, a 4-speed synchromesh gearbox with single dry plate clutch, or a fully automatic system employing a Brockhouse Turbo Transmitter. The fully automatic transmission never proved popular due to its high fuel consumption.
The brakes were of the triple servo type. Crossley also built bodywork for this chassis. Production of this model ended in 1952.