The LPTB was a quasi-public organisation akin to a modern QUANGO with considerable autonomy granted to its senior executives. It enjoyed a more or less full monopoly of transport services within its area, with the exception of those provided by the Big Four railway companies such as the Southern Railway. Consequently it was empowered to enter into co-ordination agreements with the main line railway companies concerning their suburban services. It was to a limited extent accountable to users via The London and Home Counties Traffic Advisory Committee.
Ninety-two transport and ancillary undertakings, with a capital of approximately £120 million, came under the LPTB. Central buses, trolleybuses, underground trains and trams were painted in "Underground" and "London General" red, coaches and country buses in green, with coaches branded "Green Line". Already in use on most of the tube system, "UNDERGROUND" branding was extended to all lines and stations. The name was said to have been coined by Albert Stanley, 1st Baron Ashfield in 1908 when he was General Manager of the Underground Group.
The LPTB embarked on a £35 million capital investment programme that extended services and reconstructed many existing assets, mostly under the umbrella of the 1935–1940 "New Works Programme". Although only about £21 million of the capital was spent before World War Two it allowed extensions to the Central, Bakerloo, Northern and Metropolitan lines; new trains and maintenance depots; extensive rebuilding of many central area stations (such as Aldgate East); and replacement of much of the tram network by what was to become one of the world's largest trolleybus systems. During this period two icons of London Transport were first seen: 1938 tube stock trains and the RT-type bus. Although curtailed and delayed by the outbreak of World War Two, the programme also delivered some key elements of the present overground sections of the Underground system. However, the most profound change enacted by the Board through the new works was the transition from tram to trolleybus operation alluded to earlier. In 1933 the LPTB had operated 327 route miles of tramways and 18 route miles of trolleybuses. By 1948 these totals were 102 and 255 miles respectively. The final disappearance of trams in 1952 was regretted by some sections of the staff and the public, but in terms of impact on users this was probably the most visible and dramatic change in the period.
The LPTB continued to develop the corporate identity, design and commercial advertising that had been put in place by the Underground Group. This included stations designed by Charles Holden; bus garages by architects such as Wallis, Gilbert & Partners; and more humble structures such as bus stops and shelters. The posters and advertising issued by the LPTB were often of exemplary quality and are still much sought after.
The LPTB was replaced in 1948 by the London Transport Executive under the Transport Act 1947. It was effectively nationalised, but with considerable autonomy. The LPTB continued to exist as a legal entity until wound up on 23 December 1949.