Motorways in Italy, Page 2 — Tunnels and Viaducts by Kilometre Point

The record table

How this archive measures: lengths, bores, dates and ordering

How this table is compiled

The material on this page is held in 45 captions rather than in running text, 314 words of it, each written against the image or row it belongs to by the compiler who put the page together. A crossing whose two carriageways differ in length is recorded once per direction rather than once per crossing.

A tunnel list for Italy reads differently from a neighbouring country's, because the same journey time can be bought with one long bore in one country and a dozen short ones in another. Drill-and-blast advances in rounds of a few metres, so its progress is measured in rounds per day rather than metres per hour.

Read down the length (km) column, the 95 values run from 0.1 km to 250.3 km with a midpoint at 7.8 km; the spread rather than the maximum is what says how uneven this set is. Tunnel building in Italy is shaped by geology and settlement pattern as much as by transport policy.

Only 37 of the 98 rows carry anything in the other n° (*) column, so that field describes a minority of this table and the rest of the rows are recorded without it. A concrete arch takes its load into the abutments, so it needs rock at both ends and appears where valleys are steep and narrow.

Only 36 of the 98 rows carry anything in the opening dates column, so that field describes a minority of this table and the rest of the rows are recorded without it. Comparing one national list against a neighbouring one is more informative than reading either alone, since terrain and funding practice differ sharply across borders.

Reading the figures

Together the routes listed here run about 1 697 km, an average of 17.9 km each, and the median route measures 7.8 km. The captions name 73 distinct places and structures — Nord, Tangenziale and Bologna among them — and those names are the index into the length tables where each is recorded with its own figure.

A bridge and a tunnel across the same water are rarely close in cost, and the choice is usually settled by shipping rather than by engineering. A viaduct is measured along its deck and a bridge by its main span, and confusing the two is the commonest error in a bridge list.

This page records the structures catalogued for Italy in a tunnel almanac maintained at this address since the late 1990s. Italian motorway inventories list tunnels and viaducts together in running order along the autostra-2. Seismic risk changes the lining rather than the alignment: a tunnel is among the safer places to be in an earthquake.

Abandoned bores are retained in the record, because they remain part of the engineering history of a route. Overburden decides whether a bore is driven or built in a trench, and the switch usually happens within a few hundred metres of a portal. Traffic figures are deliberately excluded, since they date far faster than the structures themselves.

Gradient inside a road tunnel is kept gentle for heavy vehicles, which lengthens the bore to gain the same height. Catenary needs headroom that a road tunnel does not, so an electrified bore is taller for the same traffic. Water management is the maintenance problem that never ends, and drainage design decides how expensive it will be.