The items given in options pertain to different aspects or functionalities of track design in railway engineering. Select the INCORRECT combination.
1
Ballast : Granular mattress laid over the earth formation to provide suitable bed for the sleepers on which they can rest
2
Ruling gradient : Maximum gradient to which a track may be laid in a particular section
3
Marshalling yard : To separate goods wagons received from various centers in the order of stations to which they are to be sent
4
Pusher gradient: Rising gradient which is followed by a falling gradient and along which the train climbs easily due to momentum gained by them over the falling gradient