Sei-kan vs Chunnel: length, opening date and class compared

• 5entries listed

Side by side

Sei-kan is recorded on data/rail.html and Chunnel on data/rail.html, compiled to the same convention, which is what makes the two figures comparable at all.

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

How this table is compiled

Sei-kan and Chunnel are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Sei-kan belongs to the 1980s and Chunnel to the 1990s, two decades in which what a tunnel had to provide by way of escape and ventilation was not the same thing.

Sei-kan is the longer of the two at 53.85 km, ahead of Chunnel at 50.45 km, a difference of 3.4 km. Driven end to end the two would run 104.3 km, which is the figure to hold against the 57.1 km of the longest single railway tunnel in the record.

That gap is about 6 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. Both rows are reachable from the railway tunnel table they were taken from, where the note column carries the tube count, the gradient and any reconstruction Sei-kan or Chunnel has had.

Across every class this archive records, Sei-kan stands 2nd by length and Chunnel 3rd, so the pair sits inside the top 3 of 244 structures. 14 other structures in this record opened within two years of Chunnel, which is the cohort it was designed alongside and the fairer comparison for how it was built.

The 1980s account for 25 entries in this archive, and Sei-kan is one of them, which is the context a single opening date does not carry on its own. Both pass ten kilometres, which 161 of the 244 structures recorded here manage, so this is a comparison inside a small group rather than across the field.

Reading the figures

Neither holds the record: Gotthard Base at 57.1 km is the longest railway tunnel recorded here, 3.25 km ahead of Sei-kan. Nothing on this page requires scripting to read. Length stands in for terrain more than for difficulty, and on a head-to-head the two crossings rarely faced the same terrain.

Both are recorded in this archive as railway tunnels, so the measurement convention is identical and the comparison is direct. Escape provision has changed more over the past forty years than excavation method has. Twin-tube crossings frequently carry two slightly different lengths, because the two carriageways rarely follow exactly the same line through the rock.

Among the railway tunnels this archive records, Sei-kan stands 2nd by length and Chunnel 3rd, adjacent in the ranking. The most useful sources are the least accessible: inspection records and commissioning documents rather than announcements. The interesting figure on most crossings is the gradient or the cover, and neither appears in a ranking by length.

1 recorded structures are longer than Sei-kan, the nearest of them Gotthard Base at 57.1 km. This archive has held per-country and per-class tunnel inventories since the late 1990s, compiled from operator and administration sources. Pumps run for the life of a subaqueous crossing and are the one system that is never switched off.

Environmental consent now outlasts construction on many schemes, and the dates in a record rarely show it. Wartime damage closed several crossings for years and a few were never reopened to their original use. Two-way traffic in one bore is what modern regulation avoids and what most older road crossings were built with.