The RT-type bus was made in greater numbers than any other London bus and became an iconic symbol of London during the 1950s and 60s, preceding the Routemaster. RT4825 is a typical example and was in service for 16 years. After it had been withdrawn, it became a training bus for drivers until 1977. From 1935, London Transport worked with Associated Equipment Company to design a new double-decker bus to replace the worn out existing vehicles. The result was the cheaper and more efficient RT-type, which was standardised so the bodies could be interchangeable with any chassis. This allowed them to be produced on a huge scale and overhauled more efficiently at Aldenham Works in north London.