Section 16(3) in The Delhi Metro Airport Express Line, General Rules, 2010
(3)Depot Signals- (i) in depots, fixed signals shall be color light type using red and yellow aspects which should be used in the manner as specified below:(ii)a "Red" aspect indicates that a train must be brought to STOP short of the signal;(iii)a "Yellow" aspect indicates that the route is set, locked and clear and a train may proceed in "Restricted manual" mode as far as the line is clear and the train operator must keep a good look out for any obstruction;(iv)the Depots shall be isolated from the running line through an approved means.
