Sandoy vs Tokyo Aqua: length, opening date and class compared

• 5entries listed

Side by side

Sandoy is recorded on data/subsea.html and Tokyo Aqua on data/subsea.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

Both rows are reachable from the subaqueous tunnel table they were taken from, where the note column carries the tube count, the gradient and any reconstruction Sandoy or Tokyo Aqua has had. Where a structure has been lengthened by a later extension the current figure is the one recorded, with the original noted alongside it.

That gap is about 11 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. This archive separates 4 classes of structure and both entries here are indexed under subaqueous tunnel, which decides the table each is ranked in and the convention its length was measured by.

Sandoy is the longest subaqueous tunnel in this archive, which makes this comparison one against the record itself rather than two entries below it. Driven end to end the two would run 20.38 km, which is the figure to hold against the 10.8 km of the longest single subaqueous tunnel in the record.

Sandoy and Tokyo Aqua are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. The 1990s account for 28 entries in this archive, and Tokyo Aqua is one of them, which is the context a single opening date does not carry on its own.

Across every class this archive records, Sandoy stands 143rd by length and Tokyo Aqua 162nd, so the pair sits inside the top 162 of 244 structures. 23 other structures in this record opened within two years of Sandoy, which is the cohort it was designed alongside and the fairer comparison for how it was built.

Reading the figures

Sandoy is the longer of the two at 10.8 km, ahead of Tokyo Aqua at 9.58 km, a difference of 1.22 km. Counting every class, 18 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.

Sandoy passes ten kilometres and Tokyo Aqua does not, which puts them in different operating regimes for ventilation and escape whatever the raw difference in metres says. 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.

Among the subaqueous tunnels this archive records, Sandoy stands 1st by length and Tokyo Aqua 2nd, adjacent in the ranking. 141 recorded structures are longer than Sandoy, the nearest of them Pianoro at 10.84 km. Cross-border schemes require two states to fund the same hole at the same time, which is why they take decades.

Two crossings of the same length built fifty years apart are different objects and only the number is comparable. The loading gauge sizes a railway bore, and a tunnel built for one country's stock can refuse another's. A single-bore crossing has to be closed to be maintained, which turns routine work into a route closure.

Sandoy was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. Blank cells mean the value is not on record. Water under pressure delays a heading more reliably than distance does, and it appears in no ranking. Both figures come from the same archive and the same convention.