In 1970, the North London DC lines and the Class 501 EMUs used on these services were converted for third-rail operation, with the fourth rail generally being removed on sections not used by London Underground (LUL). Some fourth rail was retained in the Gunnersbury and Queens Park areas for emergency use by LUL. With the closure of Broad Street, the North London Line was joined with the Stratford to North Woolwich line; this was electrified with third rail and overhead line as far as Stratford, third rail to North Woolwich. Two branches of the Watford DC Line have been closed: to Rickmansworth in 1952 (to passengers, to goods in 1967) and to Croxley Green in 1996.