Originally built as a metre-gauge line, the Bolan Pass Railway was reconstructed as a broad-gauge section in the 'nineties. It is eighty-six miles long, and the aggregate rise from Sibi, at the foot of the incline, to Kolpur, the summit before reaching Quetta, is 5,463 vertical feet. This great ascent necessitates long stretches graded at 1 in 25 and 1 in 33—throughout both of which the line is double—as well as climbs of 1 in 40 and easier gradients.
The line, which is steam operated, is solidly built, so that the heaviest engines can run over it. For many years the only Indian broad-gauge "Mallet" compound—having the 2-6-0 + 0-6-2 wheel arrangement—and a heavy 2-6-2 + 2-6-2 Garratt locomotive were used on the Bolan line to supplement the standard superheated "H.G." class 4-8-0 "maids-of-all-work." The latter haul the mails, passenger trains, and goods trains indiscriminately, assisted up the 1 in 25 and 1 in 33 lengths by powerful 2-8-2 side tank locomotives weighing some 95-1/2 tons. They have 20 in. by 26 in. cylinders, 4 ft. 3 in. coupled wheels, a grate area of 30 sq. ft. and a total heating surface of just over 2,000 sq. ft. ; 70-1/2 tons are available for adhesion and 2,200 gallons of water and 6-1/2 tons of coal are carried. Although the Mushkaf-Bolan section is in Baluchistan, the barren, rocky mountains through which it climbs are typical of "the Frontier." Sibi, at its foot, is probably the hottest spot in all India, and the shade temperature on the station platform goes up to 130° F. On the other hand, the Quetta district in winter experiences cold down to 15° of frost. The difference in the climate, atmosphere, and temperature as one travels up this wonderful railway is very marked indeed at almost any time of the year.
