density inner eastern suburbs and opened in 1979. Rolling stock All suburban passenger trains in Sydney are electric multiple units. Upon electrification in the 1920s Sydney operated single-deck multiple units, but these were progressively withdrawn from the 1960s until their demise in 1993. Single-deck automatic trains were reintroduced to Sydney in May 2019, with the completion of the Sydney Metro Northwest. Double-deck trailer carriages were delivered to the NSW Government Railways in the 1960s, and incorporated into sets with single-deck power cars. When coupled with the double decker trailer carriages, they formed the world's first fully double decker electric multiple unit trains. The majority of suburban passenger trains in Sydney today are double-deck multiple units. Depots Electric cars are maintained at depots at Hornsby in the northern suburbs, Mortdale in the southern suburbs, and Flemington in the western suburbs. A depot at Punchbowl in the southwest closed in 1994 and has since been demolished. These four depots were all built and opened with the opening of electrified services in the 1920s. Heavy maintenance of passenger cars was carried out at the Electric Carriage Workshops, Chullora and Suburban Car Workshops, Redfern. Heavy maintenance is now contracted out to Maintrain, a UGL Rail subsidiary, with workshops at Clyde. Freight services Freight services operate over most of the suburban railway lines in Sydney, however due to the high frequency of passenger services and the lack of freight only tracks, there is a curfew on freight movements during peak hours. The major interstate freight routes are the Main Southern and Main North lines, with the Illawarra and Main Western lines serving lineside industries and as alternate interstate routes. In the inner city area the Metropolitan Goods lines connects major freight terminals to the main passenger lines and the Southern Sydney Freight Line which runs parallel to the Main South line from the western end of the Metropolitan Goods lines to a point beyond the end of suburban services. The Northern Sydney Freight Corridor is a series of projects along the Main Northern line between Sydney and Newcastle aimed at increasing the number of freight trains operating along the route, by separating passenger and freight traffic. The main traffic is containerised freight. The main intermodal terminal are at Leightonfield, Yennora and Minto. Interstate trains to Sydney terminals are up to long, while short-haul container trains from the terminals to the Port Botany seaport are around