Tunnels and Viaducts on the A58 Motorway in Italy, by Kilometre Point

The record table

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

How this table is compiled

Read down the direction a1 column, the 17 values run from 39 to 1 064 with a midpoint at 85; the spread rather than the maximum is what says how uneven this set is. A structure renamed after an opening keeps both names in circulation, and the older one persists in the literature for years.

Read down the direction a4 column, the 17 values run from 39 to 1 032 with a midpoint at 85; the spread rather than the maximum is what says how uneven this set is. A tunnel boring machine produces a circular bore, which is why cross-section area and length do not scale together across entries.

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. Water ingress is pumped out continuously on a subaqueous crossing, and the pumps are the one system that can never be off.

This page records the structures catalogued along the A58 in Italy, in a tunnel almanac maintained at this address since the late 1990s. The note column records 6 exits and 3 motorway connections along the route, in running order rather than by size. Italian motorway inventories list tunnels and viaducts together in running order along the A58.

The kilometre point is recorded for each structure on the A58, which is how the operator identifies it. A crossing whose two carriageways differ in length is recorded once per direction rather than once per crossing. Two crossings of the same length built fifty years apart are different objects, and only the number is comparable.

Reading the figures

Tunnel building in Italy is shaped by geology and settlement pattern as much as by transport policy. Spain's high-speed rail programme produced a decade of tunnelling that has no parallel in its road figures. Legging a boat through an unlined canal bore was normal practice for a century and left marks on the walls that survive.

Box girders replaced trusses on medium spans because they are stiffer in torsion and cheaper to maintain. Nothing on this page is estimated; a value that could not be sourced is left blank instead. Salt water attacks reinforcement in a way fresh water does not, so subsea linings are specified to a different standard.

A tunnel outlasts the traffic it was designed for, and most of the cost after opening is ventilation and lighting rather than structure. A tunnel's gradient is often the more interesting figure, particularly on subsea and base tunnels. Toll plazas sit outside portals rather than inside them, for ventilation reasons as much as for traffic ones.

Italy's motorway network runs the length of a mountainous peninsula, which is why its structure count is so far ahead of its area. A ranking answers the question people arrive with and rarely the one they leave with. Subsea tunnels are usually built with a low point well below sea level and pumped continuously.

Base tunnels replaced summit routes that climbed with spirals and switchbacks, and several of those older lines are still in place above them. Glacial till is loose, wet and unpredictable, and the Scandinavian entries that took longest were rarely the ones through granite. The tail of a list is where the ordinary infrastructure sits, and it is more representative of what gets built than the head is. Abandoned bores are retained in the record, because they remain part of the engineering history of a route.