Arlberg vs Daliangshan No: length, opening date and class compared

• 5entries listed

Side by side

Arlberg is recorded on data/tun10.html and Daliangshan No 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

That gap is about 1 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 Arlberg or Daliangshan No has had.

Neither holds the record: Laerdal at 24.51 km is the longest road tunnel recorded here, 8.99 km ahead of Arlberg. 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.

Arlberg and Daliangshan No are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Driven end to end the two would run 30.88 km, which is the figure to hold against the 24.51 km of the longest single road tunnel in the record.

Arlberg is the longer of the two at 15.52 km, ahead of Daliangshan No at 15.37 km, a difference of 0.15 km. 16 other structures in this record opened within two years of Daliangshan No, which is the cohort it was designed alongside and the fairer comparison for how it was built.

Across every class this archive records, Arlberg stands 62nd by length and Daliangshan No 65th, so the pair sits inside the top 65 of 244 structures. Counting every class, 2 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.

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. 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.

Both are recorded in this archive as road tunnels, so the measurement convention is identical and the comparison is direct. Metres are the unit throughout. Comparing two tunnels on length alone is the question most readers ask and the least informative answer available, which is why the differences that matter are set out below.

Among the road tunnels this archive records, Arlberg stands 8th by length and Daliangshan No 9th, adjacent in the ranking. 61 recorded structures are longer than Arlberg, the nearest of them Guanshan at 15.55 km. The rock between the portals decides the programme, and two bores of equal length through different geology are different projects.

The tail of a record is more representative of what gets built than its head is. Toll revenue is usually pledged against the debt that built the crossing, and the toll ends when the debt does. Base tunnels replaced summit lines that climbed by spiral and switchback, and several of those older routes survive above them.

Daliangshan No was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. Cross-passage spacing, fixed firefighting and emergency ventilation control are what modern tunnel safety regulation actually governs. Both structures link to their own class table. Escape provision has changed more over the past forty years than excavation method has.