Mont-Blanc / Monte Bianco vs Fréjus: length, opening date, class

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Side by side

Mont-Blanc / Monte Bianco is recorded on data/tun10.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

Mont-Blanc / Monte Bianco opened in 1965 and Fréjus 15 years later in 1980, and that gap usually matters more than the length difference. 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 Mont-Blanc / Monte Bianco or Fréjus has had.

A 15-year gap spans real changes in ventilation, escape provision and excavation method, so the two were not built to the same standard. 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.

That gap is about 10 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. Driven end to end the two would run 24.51 km, which is the figure to hold against the 24.51 km of the longest single road tunnel in the record.

The 1960s account for 6 entries in this archive, and Mont-Blanc / Monte Bianco is one of them, which is the context a single opening date does not carry on its own. A crossing driven from both ends meets in the middle, and the survey needed to make that happen is invisible in the finished figure.

Mont-Blanc / Monte Bianco and Fréjus are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. 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

Fréjus is the longer of the two at 12.9 km, ahead of Mont-Blanc / Monte Bianco at 11.61 km, a difference of 1.29 km. Counting every class, 12 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.

Across every class this archive records, Fréjus stands 110th by length and Mont-Blanc / Monte Bianco 123rd, so the pair sits inside the top 123 of 244 structures. 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.

Mont-Blanc / Monte Bianco predates the safety regulation written after the fires of 1999 to 2001, and was retrofitted rather than designed to it. Nothing in either row is estimated: a value that could not be corroborated is left blank rather than filled in. Linings are inspected on a cycle of years and repaired in windows of hours.

109 recorded structures are longer than Fréjus, the nearest of them Hsuehshan at 12.94 km. Two crossings of the same length built fifty years apart are different objects and only the number is comparable. Trade reporting is faster than official publication and less reliable, which is why opening dates sometimes move after the event.

6 recorded road tunnels fall between them by length, the nearest being Guigala at 12.79 km. The note column carries the qualifications. The loading gauge sizes a railway bore, and a tunnel built for one country's stock can refuse another's. A record for length has changed hands roughly once a decade since the 1870s.