The first prototype Routemaster made it's debut in 1954, this new vehicle was designed by LT and was intended to build on the success of the earlier RT, RM1 originally appeared with a solid front grille, however by the time it and the second prototype finally entered passenger service in 1956, both had received a revised front radiator grille that bore a closer resemblance to the actual production vehicles. The Routemaster was the successor to the RT, and like in predecessor it was designed by London Transport to handle the rigors of service in the capital. The first production vehicles entered service in 1959, replacing trolleybuses at Popular and West Ham garages. In all over 2100 standard length Routemasters entered service between 1959 and 1964.