Middlesbrough Corporation Tramways Department commenced direct operation of local passenger transport in 1921 in succession to the Imperial Tramways Company Limited, and ceased in 1968 when the Corporation itself was subsumed into the new Teesside County Borough authority. Tramcars were the main form of traction for the first ten years, but they finally ceased in 1934. Trolleybuses were considered but not adopted, despite the authority's involvement (from 1919) in the system of the Tees-Side Railless Traction Board (q.v.). Motor buses were insignificant at first, yet in due course they not only replaced the tramcars but were the means of a vast expansion to levels of service and efficiency which were previously unimaginable. This was largely the work of the legendary General Manager, Frank Lythgoe, who took office three months after the last tram, and remained until his retirement in 1964. The department's title was changed from 'Tramways' to 'Transport' in 1933 and the Transporter Bridge was directly operated by the Transport Department from 1936.

Operation commenced on 4th April 1921 with thirty-one tramcars and five motor buses acquired with the Corporation's share of the Imperial Tramways undertaking, augmented by six new motor buses bought in readiness. Trams were operated jointly with Stockton and Thornaby Corporations between North Ormesby and Norton Green, and separately between the Transporter and Linthorpe. Buses ran from the Exchange to Grove Hill and to Stokesley and new services from Port Clarence (Transporter) to Seaton Carew (joint with West Hartlepool Corporation) and to Haverton Hill were commenced at once.

In the first year, nine new top-covered double-deck tramcars and two more motor buses were purchased, the single deck trams were re-equipped, a large new tram and bus depot was built at Parliament Road, and the single track in Grange Road was doubled. The next year saw further track doubling and renewals. The town was extending rapidly, but the tramway system was never to reach further than it had done in 1901. This, despite the improvements, was to be its undoing. The shortcoming was most acutely felt at North Ormesby, where the trams stopped short at the end of Borough Road East on account of the level crossing. Later housing development at Linthorpe and Acklam had the same effect, with buses introduced to serve the new areas, taking traffic away from the trams, yet not making a profit themselves.

A Queens's Square to North Ormesby bus service was introduced in 1926, but by 1927 the Corporation had withdrawn from the Haverton Hill, Stokesley and Seaton Carew services. The indication of services by letters commenced in 1927 and remained a distinctive characteristic of the undertaking until the end. In that year, services A and B were introduced to Acklam, C and D to Grove Hill and E and F to North Ormesby, each pair being a circular showing one letter clockwise and the other anti-clockwise. A service to Brambles Farm was introduced in 1931, letter unknown but possibly G, and the letter H was allocated to the Marton service, which was the remnant of the Stokesley service. Double-deck buses had been introduced in 1929, and their numbers were greatly increased in 1931. They took over from the trams between Norton and North Ormesby on New Year's Day 1932, the route being lettered O and immediately extended to North Ormesby Market Place. At the other end of the route, some journeys were soon extended to Ashville Avenue. Also in 1932 a Stockton via Acklam service commenced, numbered 11: like the O, it was jointly run with Stockton Corporation, but not with Thornaby Corporation, who had sold their tramway interests to Stockton in 1930. A Newport to Oxford Road circular was also introduced in 1932, lettered J and K.

In 1934, the opening of the Newport Bridge led to the extension of service 11, to operate Stockton-Acklam-Middlesbrough-Billingham (Greenwood Road). Futher double deck deliveries that year, this time of the 'lowbridge' style to negotiate Albert Bridge, enabled the remaining tram route to close on 9th June, replaced by bus services M and P. The M extended beyond Linthorpe to Oxford Road End but the P did not. At the same time a revised J and K circular linked Newport, Cambridge Road and Grove Hill, while the E and F incorporated the Brambles Farm service. Fleet renewals between 1934 and 1940 enabled double-deck buses to replace single-deckers on all the town services. A revised A and B service, not now a circular, was extended to Mandale Road in 1935 and to Hall Drive in 1936; buses showed letter B to Acklam and A to Exchange. Also in 1935 the P service was extended to Thornfield Road, and in 1937 the M was extended alternately to Lodore Grove and Levick Crescent. A new B service via Green Lane to Brookfield was introduced in 1938. The 'Panther Service' operating to Seamer was taken over on New Year's Day, 1939 and later took the letter S.

The second world war (1939-1945) was a period of austerity and restraint, and a reduced 11 service was split at Middlesbrough, and stayed that way. Rapid growth re-commenced after the war, with service A extended to Malvern Drive in 1946 and a new service G introduced to Thorntree (Ruth Avenue). The busiest year was 1949, with the start of services I to Saltersgill, L (Link) from West Lane via Ladgate Lane to Brambles Farm, T to Tollesby and Y to Thorntree (Greenway). In 1952 services E and F were separated, and in 1953 the Q and R circular replaced the I service. Service N commenced to Berwick Hills in 1953 and was extended in 1955. Service U to Park End was introduced in 1954, and the Z to Park End via Marton Road in 1957, in which year the Billingham 11 was extended to Rievaulx Avenue. The U and Z operated as a circular from 1960, though without through fares across the outer terminus. The B was extended to Stainton in 1961 and the Z diverted to Easterside from 1963. Some journeys on service O were diverted to Blue Hall at Norton in 1965, but reverted to Norton Green in 1966. Also in 1966 a new service commenced jointly with Stockton Corporation (who provided the vehicles) between Middlesbrough and Thornaby (New Town Centre) via Acklam, and finally the A service was extended, despite sustained objections, to the Oval, Brookfield.

In the period 1966-1968, many other substantial alterations were discussed, planned and agreed, but none came into effect until after the Middlesbrough authority had been absorbed into Teesside on 1st April, 1968.

Philip Battersby

Livery of the undertaking's vehicles

The tram-cars acquired from Imperial Tramways were subsequently painted dark blue and cream,with chocolate underframes
Early motor buses were blue with cream upper panels but later deliveries had unpainted aluminium lower panels, to make repair easier.
From 1936 Mr Lythgoe introduced a new livery of Middlesbrough Blue, with two county cream bands. The whole was enhanced by gold lining and a narrow black band separating the colours. Crests were carried on both upper and lower deck sides and on the rear panels. Later versions had only the lower cream band.
Turquoise and cream (the cream bands were lined in blue) was introduced in 1966 in advance of the Teesside amalgamation