The utility double decker was a product developed during the Second World War to counter the growing shortage of double deck buses.
Most bus production had been halted or highly restricted during the early war years, with bus chassis manufactures and body builders being instead involved in production of essential military equipment.

However it soon became clear that the combination of enemy action, aging vehicles, and shortages of parts was affecting operators ability to maintain services.
The Ministry of Supply thus allowed selected manufactures, including Guy, Bristol, Daimler and Leyland to produce bus chassis', while a limited number of bodybuilders were allowed to build bodies to a highly restrictive specification. These bodies were built using un-seasoned timber, limited interior paneling, and the design also omitted any non essential radiussed sections, allowing a saving in scarce materials and labour time. From the passengers point of view, comfort wasn't a high priority, as most of the vehicles were supplied with rather basic wooden slated seats.

These buses were allocated by the Ministry to operators on a need to have bases, with various combinations of body and chassis types appearing in many urban fleets across the country.

The poor quality materials used in the utility bodies, meant that most had a short life in their original form. During the 1950's many operators re-bodied or withdraw these vehicles has soon as possible.

The Utility type was used by London Transport between 1942 and the the early 1950's. Deliveries included 9 Bristol K5, 281 Daimler CWA6 / CWD6, and 435 Guy Arabs, some of the later deliveries had less austere styling, which allowed radiussed rear roof domes.

Virtually all the London vehicles were used on Central Area routes, although some Daimlers did find their way onto the Green Line network when it was re-introduced following its wartime suspension.

The OOC model can be produced in several different versions, Guy Arab, Daimler CW, Leyland STD, Bristol K or AEC Regent, the first releases occurred in 1999 and a steady flow of new issues has continued ever since.