Zhongnanshan vs Laerdal: length, opening date and class compared

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Side by side

Zhongnanshan is recorded on data/tun10.html and Laerdal 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

Zhongnanshan and Laerdal 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 42.55 km, which is the figure to hold against the 24.51 km of the longest single road tunnel in the record.

Laerdal is the longer of the two at 24.51 km, ahead of Zhongnanshan at 18.04 km, a difference of 6.47 km. 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 Zhongnanshan or Laerdal has had.

Both belong to the 2000s, so the two were specified against the same expectations and the length difference is not standing in for a change of era. 31 other structures in this record opened within two years of Zhongnanshan, which is the cohort it was designed alongside and the fairer comparison for how it was built.

Across every class this archive records, Laerdal stands 20th by length and Zhongnanshan 44th, so the pair sits inside the top 44 of 244 structures. Counting every class, 23 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.

The 2000s account for 53 entries in this archive, and Laerdal 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

That gap is about 26 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. The fires at Mont Blanc, in the Tauern and in the Gotthard between 1999 and 2001 rewrote European tunnel safety, and every structure opened since reflects that.

At over twenty kilometres Laerdal sits in the small group of bores long enough to need intermediate ventilation and a full escape regime. Laerdal is the longest road tunnel in this archive, which makes this comparison one against the record itself rather than two entries below it. A record only moves when one project completes.

Both are recorded in this archive as road tunnels, so the measurement convention is identical and the comparison is direct. Adding a metre to the longest tunnel in the world costs what adding a kilometre to an ordinary one does. Escape provision has changed more over the past forty years than excavation method has.

Among the road tunnels this archive records, Zhongnanshan stands 4th by length and Laerdal 1st, 3 places apart. 2 recorded road tunnels fall between them by length, the nearest being Tianshan Shengli at 22.13 km. Fixed links change settlement patterns, so the traffic a crossing carries later is not the traffic that justified it.

19 recorded structures are longer than Laerdal, the nearest of them Pajares Base at 24.6 km. A single-bore crossing has to be closed to be maintained, which turns routine work into a route closure. Structures still under construction cannot hold a record here, and are listed separately until they carry traffic.