Navigation Canal Tunnels by Length, Part 2 — a Ranked Reference List

• 28entries listed
• 0.88 kmlongest bore
• 1815–1819openings span
• 8.84 kmtotal length

The record table

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

How this table is compiled

This page records the canal tunnels catalogued for the world in a tunnel almanac maintained at this address since the late 1990s. Laid end to end the entries on this page would run 8.84 km, which is a number with no engineering meaning but a useful sense of the scale of what is catalogued.

The median entry measures 0.24 km, so half the table sits below that and half above, which is a better guide to the typical structure here than the headline figure. The shortest recorded entry is 0.05 km against 0.88 km at the top, a spread of 16.88x across the same table.

The three longest entries alone account for 2.24 km of the 8.84 km on this page, which is 25 per cent of the total from 3 of 28 rows. 14 entries sit above the median and 14 at or below it, so the table is evenly weighted and not clustered at one end.

A new scheme in the world would have to beat 0.88 km to change the head of this table, and that is the figure worth rechecking when one opens. 5 of the 28 entries fall within a quarter of the median length, which is how tightly this particular list clusters around its typical structure.

The 28 rows for the world are ordered by length, not by date, so the 1819 opening sits well down the table without being any less current. Eighth on the list is Severnake or Bruce at 0.46 km, which is where the table stops being about record holders and starts being about ordinary infrastructure.

Reading the figures

The ten longest average 0.56 km against 0.18 km for everything below them, and that ratio is the clearest thing this table says about the distribution. The tunnel column names 29 distinct entries on this page, Islington and Saddington among them, each traceable to the operator or administration record it was taken from.

Read down the length column, the 29 values run from 48 m to 878 m with a midpoint at 228 m; the spread rather than the maximum is what says how uneven this set is. Rack railways climb where adhesion alone cannot, and their tunnels are short, steep and unlike anything on a main line.

Dated entries run from 1815 to 1819, and the busiest decade is the 1810s with 5 recorded openings. The table on this page runs to 29 rows and records Country, Tunnel, Length, Canal and Year of construction for each of them, which is the shape the original compiler chose rather than one imposed here.

Roughly 0 of the dated entries opened in this century, which is a rough measure of how much of the network is recent. Only 6 of the 29 rows carry anything in the year of construction column, so that field describes a minority of this table and the rest of the rows are recorded without it.

Between the longest and the tenth-longest the drop is 0.48 km, which is the part of the table that changes when a single scheme opens. The longest entry is 16.9 times the shortest and 3.7 times the median, which is the quickest measure of how uneven the table is.