Electric trams started running in Isleworth in 1901, from a depot situated on the north side of London Road, near the border with Hounslow. The original operating company was London United Tramways, which was subsumed into the new London Passenger Transport Board in 1933. In 1935 the depot was converted to trolleybus operation. It was designed in a horseshoe shape with a travelator at the far end, which had a turntable added for the trolleybuses. Originally known as Hounslow Depot, it was renamed Isleworth and given the code "IH" in 1950. It had a capacity for 37 vehicles and only ever operated one service: the 57 tram route which, on conversion, became the 657 trolleybus route. Both the 57 and 657 operated between Hounslow and Shepherd's Bush Green via Isleworth, Brentford, Chiswick, and Goldhawk Road. From 1902 the Hounslow terminus of the 57 tram was the "Hussar" in Staines Road, Hounslow Heath. In July 1922 the service was cut back to terminate at the "Bell" at the western end of Hounslow High Street. A special turning place half a mile along Staines Road, at its junction with Wellington Road, was built for the 657 trolleybus. At different times there were ambitious plans to extend the tram lines westward to Staines-upon-Thames and even to Maidenhead, but these never came about and the modern replacement motor bus route 237 traverses exactly the same roads between Hounslow Heath and Shepherd's Bush as the trams did over 110 years ago (with a short extension to White City).