Heavily oil stained, 5 feet 6 inch gauge 3831 built in the 1950s as an ALCO DL500 leaves Kolpur with the "Chiltan Express", 1000 Lahore to Quetta. Kolpur is the top of the tortuous Bolan Pass much of which is 1 in 25 (4%) grade. All trains require helper locos on this climb.