Section 16(4)(viii) in The Delhi Metro Airport Express Line, General Rules, 2010
(viii)each Delhi Metro Airport Express Line employee involved in the shunting of work trains, the operation of work trains at a maintenance site and the operation of work trains within an Engineer's Possession, shall carry a hand lamp capable of displaying Red, Green and White aspects in working order and shall be conversant with its proper use and in addition, he shall also carry a Red flag and a Green flag.