Section 50(1)(iii) in The Delhi Metro Airport Express Line, General Rules, 2010
(iii)in case it is more convenient to provide assisting train from the leading end direction, the Traffic Controller shall instruct the train operator of the assisting train to change the cab and proceed in the direction of the stalled train under Coded manual mode as far as limit of authority under cab signaling and thereafter change to Restricted manual mode and stop short of about ten meters of stalled train;