Road Tunnels in Japan — 64 Listed by Length

• 64entries listed
• 11.06 kmlongest bore
• 1957–2010openings span
• 277.62 kmtotal length

The record table

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

How this table is compiled

The three longest entries alone account for 31.35 km of the 277.62 km on this page, which is 11 per cent of the total from 3 of 63 rows. After the 1980s the next busiest decade here is the 1990s with 20 openings, so the building effort came in more than one wave.

Where one of these 63 lengths disagrees with an operator's own figure for Japan, the table keeps the published value and notes the difference instead of averaging the two. The 63 rows for Japan are ordered by length, not by date, so the 2010 opening sits well down the table without being any less current.

A new scheme in Japan would have to beat 11.06 km to change the head of this table, and that is the figure worth rechecking when one opens. The longest entry is 3.7 times the shortest and 3.0 times the median, which is the quickest measure of how uneven the table is.

13 of the 63 measured entries exceed five kilometres, and those are the ones that carry a full ventilation and escape regime. Laid end to end the entries on this page would run 277.62 km, which is a number with no engineering meaning but a useful sense of the scale of what is catalogued.

Second and third place go to Hida at 10.71 km and Tokyo Aqua at 9.58 km. The table on this page runs to 64 rows and records Tunnel, Length (m), Year of opening, Prefec. and Notes for each of them, which is the shape the original compiler chose rather than one imposed here.

Reading the figures

This page records the road tunnels catalogued for Japan in a tunnel almanac maintained at this address since the late 1990s. The year of opening column runs from 8 to 2012 across 50 dated rows, and the 1980s alone account for 21 of them, so the building effort here came in waves rather than evenly.

Dated entries run from 1957 to 2010, and the busiest decade is the 1980s with 21 recorded openings. The material on this page is held in 17 captions rather than in running text, 165 words of it, each written against the image or row it belongs to by the compiler who put the page together.

Roughly 4 of the dated entries opened in this century, which is a rough measure of how much of the network is recent. The captions name 20 distinct places and structures — Circular, Route and Tokyo among them — and those names are the index into the length tables where each is recorded with its own figure.

The dated entries carry 25 distinct opening years across 53 years, and the median opening year is 1989. They are not uniform: the fullest runs to 23 words and the briefest to 6, and on a page of this kind the long ones are where the explanation lives — the caption carries what the picture cannot.

Eighth on the list is Higo at 6.34 km, which is where the table stops being about record holders and starts being about ordinary infrastructure. The tunnel column names 64 distinct entries on this page, Kan-etsu (south bound) and Hida among them, each traceable to the operator or administration record it was taken from.