Shenzhen vs Lötschberg: length, opening date and class compared

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Side by side

Shenzhen is recorded on data/rail.html and Lötschberg 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

Shenzhen and Lötschberg are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Shenzhen belongs to the 2010s and Lötschberg to the 2000s, two decades in which what a tunnel had to provide by way of escape and ventilation was not the same thing.

Shenzhen is the longer of the two at 35.66 km, ahead of Lötschberg at 34.58 km, a difference of 1.08 km. Driven end to end the two would run 70.23 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 3 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 Shenzhen or Lötschberg has had.

Across every class this archive records, Shenzhen stands 7th by length and Lötschberg 8th, so the pair sits inside the top 8 of 244 structures. 14 other structures in this record opened within two years of Shenzhen, which is the cohort it was designed alongside and the fairer comparison for how it was built.

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

Both are recorded in this archive as railway tunnels, so the measurement convention is identical and the comparison is direct. Neither holds the record: Gotthard Base at 57.1 km is the longest railway tunnel recorded here, 21.45 km ahead of Shenzhen. Salt water attacks reinforcement differently from fresh, and subsea linings are specified accordingly.

The tail of a record is more representative of what gets built than its head is. Trade reporting is faster than official publication and less reliable, which is why opening dates sometimes move after the event. A tunnel's gradient is often the more interesting figure, particularly on subsea crossings where vehicles have to climb back out.

Shenzhen was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. Among the railway tunnels this archive records, Shenzhen stands 7th by length and Lötschberg 8th, adjacent in the ranking. Two crossings of the same length built fifty years apart are different objects and only the number is comparable.

6 recorded structures are longer than Shenzhen, the nearest of them Songshan Lake at 38.81 km. A single-bore crossing has to be closed to be maintained, which turns routine work into a route closure. Cross-passage spacing, fixed firefighting and emergency ventilation control are what modern tunnel safety regulation actually governs.

Portals and approaches are counted consistently. The longer bore is not the harder job. Height above sea level is a separate record from length. A short bore beneath a city can cost more than a long one through a mountain. Linings are inspected on a cycle of years and repaired in windows of hours.