Simplon-I vs Fréjus: length, opening date and class compared

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Side by side

Simplon-I is recorded on data/rail.html and Fréjus 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

A 74-year gap spans real changes in ventilation, escape provision and excavation method, so the two were not built to the same standard. Simplon-I is 1.54 times the length of Fréjus, and it is the ratio rather than the 6.91 km that says how differently the two crossings had to be ventilated and escaped.

Simplon-I and Fréjus are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Simplon-I belongs to the 1900s and Fréjus to the 1980s, two decades in which what a tunnel had to provide by way of escape and ventilation was not the same thing.

Simplon-I is the longer of the two at 19.8 km, ahead of Fréjus at 12.9 km, a difference of 6.91 km. Driven end to end the two would run 32.7 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 35 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 Simplon-I or Fréjus has had.

Simplon-I is recorded as a railway tunnel and Fréjus as a road tunnel, so the two are measured the same way but built to different constraints. 9 other structures in this record opened within two years of Fréjus, which is the cohort it was designed alongside and the fairer comparison for how it was built.

Reading the figures

Counting every class, 74 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. Length is the dimension published most consistently across countries, which is why it governs an ordering, but it is a poor measure of the work involved.

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. 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.

Neither holds the record: Gotthard Base at 57.1 km is the longest railway tunnel recorded here, 37.3 km ahead of Simplon-I. Across every class this archive records, Simplon-I stands 35th by length and Fréjus 110th, so the pair sits inside the top 110 of 244 structures. Only structures open to traffic are compared.

This archive has held per-country and per-class tunnel inventories since the late 1990s, compiled from operator and administration sources. Environmental consent now outlasts construction on many schemes, and the dates in a record rarely show it. A base tunnel trades much greater length for a far lower summit altitude, which changes what the number means.

34 recorded structures are longer than Simplon-I, the nearest of them Simplon-II at 19.82 km. Two independent sources back every value. Ventilation arrangement caps how long a bore can be driven more directly than money does. Water under pressure delays a heading more reliably than distance does, and it appears in no ranking.