Howrah–Nagpur–Mumbai line

The Howrah–Nagpur–Mumbai line (also known as Mumbai–Kolkata line) is a railway line in India connecting Kolkata and Mumbai via Nagpur. The 1968 km railway line was opened to traffic in 1900.

Sections
The 1968 km trunk line has been treated in more detail in smaller sections:
 * 1) Howrah–Kharagpur section
 * 2) Kharagpur–Tatanagar section
 * 3) Tatanagar–Bilaspur section
 * 4) Bilaspur–Nagpur section
 * 5) Nagpur–Bhusawal section
 * 6) Bhusawal–Kalyan section
 * 7) Kalyan–Mumbai CST section

Geography
The Howrah–Nagpur–Mumbai line cuts across the central parts of India in an east–west direction and traverses the plains of lower West Bengal, the southern part of Chota Nagpur Plateau, the Deccan Plateau, the Western Ghats and finally the Western Coastal Plains.

History
The first train in India travelled from Bori Bunder in Bombay to Tannah (current Thane) on 16 April 1853. By May 1854, Great Indian Peninsula Railway's Bombay–Tannah line was extended to Callian (current Kalyan). Bhusawal station was set up in 1860 and in 1867 the GIPR branch line was extended to Nagpur.

While the entire Mumbai–Nagpur line was broad gauge, the next part from Nagpur to Rajnandgaon was metre gauge. The Nagpur Chhattisgarh Railway started construction of the 240 km Nagpur–Rajnandgaon section in 1878, after surveys were started in 1871. The Nagpur–Tumsar Road section was opened in April 1880 and the Tumsar Road–Rajnandgaon section in December 1880.

The GIPR and EIR, working jointly, completed the Howrah–Allahabad–Mumbai line thereby establishing a connection between Kolkata and Mumbai in 1870. The great famine of 1878 was an impetus for the fast completion of the Nagpur Chhattisgarh Railway track, but by then the idea of a route from Mumbai to Kolkata, shorter than the one via Allahabad, had set in.

The Bengal Nagpur Railway was formed in 1871. Amongst its major objectives were taking over of the Nagpur Chhattisgarh Railway and its conversion to broad gauge and extension of its system by a 772 km line to Asansol on EIR's main line. The entire task was completed by 1891 and Nagpur was connected to Asansol. However, the line via Asansol was never seriously used as a link to Howrah for passenger traffic.

The Sini–Kharagpur–Kolaghat line was opened in 1898–99. The Kolaghat–Howrah section was completed in 1899–1900. The entire line was opened with the completion of the bridge across the Rupnarayan River, near Kolaghat, on 19 April 1900.

Electrification
The entire line is electrified.

Speed limits
The entire Howrah–Nagpur–Mumbai line is planned to be upgraded as a "Group A" line which will enable it to take speeds up to 160 kmph. Its current speed is restricted at 130kmph. Rest are under 110 kmph.

Passenger movement
Howrah (Kolkata), Kharagpur Junction, Tatanagar Junction, Rourkela Junction, Bilaspur Junction, Raipur Junction, Durg Junction, Nagpur Junction, Badnera, Akola, Bhusawal, Nasik Road, Manmad and Kalyan (Mumbai subarban) on this line, are amongst the top hundred booking stations of Indian railway.

Golden Quadrilateral
The Howrah–Nagpur–Mumbai line is a part of the Golden Quadrilateral. The routes connecting the four major metropolises (New Delhi, Mumbai, Chennai and Kolkata), along with their diagonals, known as the Golden Quadrilateral, carry about half the freight and nearly half the passenger traffic, although they form only 16 per cent of the length.