The most important connection was the 529 kilometres (329 mi) long Calcutta–Parbatipur–Haldibari–Siliguri link first established in 1878 and then developed in stages[1] (for details see Howrah-New Jalpaiguri Line).

[2] In pre-independence days, a 581 kilometres (361 mi) long metre gauge line running via Radhikapur, Biral, Parbatipur, Tista, Gitaldaha and Golokganj connected Fakiragram in Assam with Katihar in Bihar.

[1] The 62.7 kilometres (39.0 mi) long metre gauge branch line from Malbazar in Jalpaiguri district to Changrabandha in Cooch Behar district is now made into 1,676 mm (5 ft 6 in) wide 5 ft 6 in (1,676 mm) broad gauge section in 2016 & extended 64.1 kilometres (39.8 mi) further to New Coochbehar, with train service, as per the railway time table.

The present 88.3 kilometres (54.9 mi) long metre gauge line on the Bangladesh side from Burimari to Lalmonirhat is still functional.

[3][9] The 76.5 kilometres (47.5 mi) Fakiragram-Dhubri branch line was inaugurated after gauge conversion in September 2010.