Tiantaishan vs Arlberg: length, opening date and class compared

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Side by side

Tiantaishan is recorded on data/tun10.html and Arlberg 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

Tiantaishan and Arlberg are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Tiantaishan belongs to the 2020s and Arlberg to the 1970s, two decades in which what a tunnel had to provide by way of escape and ventilation was not the same thing.

Tiantaishan is the longer of the two at 15.56 km, ahead of Arlberg at 15.52 km, a difference of 0.04 km. Driven end to end the two would run 31.08 km, which is the figure to hold against the 24.51 km of the longest single road tunnel in the record.

That gap is about 0 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 road tunnel table they were taken from, where the note column carries the tube count, the gradient and any reconstruction Tiantaishan or Arlberg has had.

Across every class this archive records, Tiantaishan stands 60th by length and Arlberg 62nd, so the pair sits inside the top 62 of 244 structures. 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.

Counting every class, 1 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. 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

The 1970s account for 12 entries in this archive, and Arlberg is one of them, which is the context a single opening date does not carry on its own. Geology decides cost and programme far more than distance does, so a shorter bore through difficult ground can be the greater achievement.

Both are recorded in this archive as road tunnels, so the measurement convention is identical and the comparison is direct. A tunnel outlives the traffic forecast that paid for it, and most of its lifetime cost is ventilation and lighting. Water management is the maintenance problem that never ends, and drainage design decides its cost.

Tiantaishan was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. Among the road tunnels this archive records, Tiantaishan stands 7th by length and Arlberg 8th, adjacent in the ranking. Two-way traffic in one bore is what modern regulation avoids and what most older road crossings were built with.

Reconstruction after a fire is recorded because it usually changes both the profile and the ventilation arrangement. The loading gauge sizes a railway bore, and a tunnel built for one country's stock can refuse another's. Catenary needs headroom a road tunnel does not, so an electrified bore is taller for the same traffic.

59 recorded structures are longer than Tiantaishan, the nearest of them Daiyunshan at 15.62 km. Two independent sources back every value. Sequential excavation is slower per metre and far more tolerant of ground that changes without warning. A national administration publishes what it maintains, so a crossing that changes owner can move between lists.