Route 505 is an MTR route linking Sam Shing stop and Siu Hong stop, in the southern and northern parts of Tuen Mun, Hong Kong, respectively. The route is coloured red on the Light Rail system map. The route has three one-way segments: and are on a one-way clockwise loop at the northern end of the line; and in the middle of the route there is a split such that and are only served by northbound trains, and only by southbound trains. The route began service on 24 September 1988, from Siu Hong to . At the time, the trains towards Siu Hong had a different number, 504. From 2 February 1992, the route was extended to . Stops (Tuen Mun station) (to Siu Hong only) (to Siu Hong only) (to Sam Shing only) (to Siu Hong only) (Siu Hong station) 505