Railway Tunnels in India — Complete List by Length

• 32entries listed
• 1903–1998openings span
• 28.59 kmtotal length

The record table

How this archive measures: lengths, bores, dates and ordering

How this table is compiled

Roughly 0 of the dated entries opened in this century, which is a rough measure of how much of the network is recent. Openings average one every 3.2 years across the dated entries here, though they arrive in clusters, not at that rate. Railway tunnel lengths are taken along the track centre line.

A freight route's ruling gradient is set by the heaviest train it must lift, and that single figure decides whether a tunnel is needed at all. A ranking of this kind moves whenever a single large scheme opens, and nothing on a stale page announces that a longer structure now exists elsewhere.

The 1990s account for 27 openings here and the 1900s for 4, so the building effort was not spread evenly across the period. Single-track bores built as a pair are recorded individually, since treating them as one structure would misstate both the engineering and the cost. A referendum has stopped more alpine schemes than geology has.

Tunnel building in India is shaped by geology and settlement pattern as much as by transport policy. A projected opening date is a forecast, and on large schemes forecasts have historically slipped by years. A railway tunnel is sized by the loading gauge, and a bore built for one country's rolling stock can refuse another's.

Gradient inside a road tunnel is kept gentle for heavy vehicles, which lengthens the bore to gain the same height. Administrative boundaries have been redrawn in several countries since these lists were first assembled. The oldest entries in any national list are usually canal or rail, because roads were the last mode to need long bores.

Reading the figures

Toll revenue on a fixed link is usually pledged against the debt that built it, and the toll ends when the debt does. Gradient limits are the main reason rail tunnels run longer than road tunnels on the same crossing. A ranking answers the question people arrive with and rarely the one they leave with.

Nineteenth-century tunnels were surveyed from the surface with theodolites and chains, and the best of them met within centimetres. A record is a statement about what has been published, not about what exists. Trade press reporting is faster than official publication and less reliable, which is why an opening date sometimes moves after the event.

Escape and rescue provision has driven most of the change in tunnel design over the past three decades. A hard shoulder inside a tunnel is expensive width, and its absence is why breakdowns are treated as emergencies. Widening an existing bore is rarely economic, so capacity is usually added by driving a second one alongside.

The fires of the late 1990s and early 2000s reshaped European tunnel safety regulation permanently. Dates before 1900 are frequently approximate, and are shown as published, unreconciled. Traffic signals inside a tunnel exist to stop vehicles entering behind an incident, and they are the cheapest safety system on the list.

Some entries carry a range instead of a single value where the two carriageways differ. The first railway tunnels were driven by hand and gunpowder, and their alignments still carry the marks of both. The note column is often the most useful part of a row, recording tube counts, gradients, closures and reconstruction dates.