St. Gotthard / San Gottardo vs Tiantaishan: length and opening date

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Side by side

St. Gotthard / San Gottardo is recorded on data/tun10.html and Tiantaishan on data/tun10.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

Among the road tunnels this archive records, St. Gotthard / San Gottardo stands 6th by length and Tiantaishan 7th, adjacent in the ranking. The median road tunnel in this archive measures 12.46 km, so both entries here are well clear of the ordinary case and the comparison is between two outliers rather than two typical crossings.

A 41-year gap spans real changes in ventilation, escape provision and excavation method, so the two were not built to the same standard. The 1980s account for 25 entries in this archive, and St. Gotthard / San Gottardo is one of them, which is the context a single opening date does not carry on its own.

This archive separates 4 classes of structure and both entries here are indexed under road tunnel, which decides the table each is ranked in and the convention its length was measured by. Spoil from a long bore is a civil work of its own, and outside several alpine portals it has become a permanent landform.

That gap is about 8 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. Driven end to end the two would run 32.5 km, which is the figure to hold against the 24.51 km of the longest single road tunnel in the record.

St. Gotthard / San Gottardo and Tiantaishan are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. 19 other structures in this record opened within two years of Tiantaishan, which is the cohort it was designed alongside and the fairer comparison for how it was built.

Reading the figures

St. Gotthard / San Gottardo is the longer of the two at 16.94 km, ahead of Tiantaishan at 15.56 km, a difference of 1.38 km. Counting every class, 9 recorded structures fall between these two by length; the comparison is a window on that part of the record rather than a gap in it.

Across every class this archive records, St. Gotthard / San Gottardo stands 50th by length and Tiantaishan 60th, so the pair sits inside the top 60 of 244 structures. 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.

St. Gotthard / San Gottardo opened in 1980 and Tiantaishan 41 years later in 2021, and that gap usually matters more than the length difference. Neither holds the record: Laerdal at 24.51 km is the longest road tunnel recorded here, 7.57 km ahead of St. Gotthard / San Gottardo. Length is measured portal to portal.

Tiantaishan was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. A tunnel's gradient is often the more interesting figure, particularly on subsea crossings where vehicles have to climb back out. The oldest crossings still carrying traffic were built before any of the codes that now govern their upkeep.

Depth below sea level is recorded where published. A record for length has changed hands roughly once a decade since the 1870s. Motorway crossings are usually twinned, and the second bore is often driven decades after the first. Widening an existing bore is rarely economic, so capacity is added by driving a second one alongside.