The rail line goes across a total length of 44.98 kms crossing as many as 19 bridges and 14 tunnels. The tunnels on the route covers a total length 38.55 kms, with the longest tunnel covering 5270 metres and the smallest tunnel covers 538 metres. Interestingly, these tunnels cover almost 85% of the total journey.

https://www.financialexpress.com/infrastructure/railways/indian-railways-new-sivok-rangpo-rail-project-travel-from-west-bengal-to-sikkim-in-just-2-hours-watch-video/1691100/lite/