We are brother and sister of our zone.. We both share our rakes.. If in our UP journey one of us gets late, the Down train is re-scheduled. RSA exsists between us.. We both are two main trains of our zone.. We run to a Metropolian city but spend only two hour halting at the main station of Metropolian city and return to our home city quickly due to our RSA.. Guess, the trains and the zone...