Tunnels and Viaducts on the A08 Motorway in Italy, by Kilometre Point

• 1entries listed
• 0.08 kmlongest bore
• 0.08 kmtotal length

The record table

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

How this table is compiled

30 rows are rendered in total, so 29 of them carry a note or a blank where a length belongs and are shown without being counted. Where one of these 1 lengths disagrees with an operator's own figure for Italy, the table keeps the published value and notes the difference instead of averaging the two.

Laid end to end the entries on this page would run 0.08 km, which is a number with no engineering meaning but a useful sense of the scale of what is catalogued. A canal tunnel is sized by the boat, not by the traffic, which is why the oldest of them are so narrow.

The table on this page runs to 5 rows and records Tunnel / Viaduct, Direction Varese, Direction Milano and Notes for each of them, which is the shape the original compiler chose rather than one imposed here. Compressed-air working let shafts be sunk through water-bearing ground and cost the health of the men who did it.

The entries sum to roughly 0.08 km of bore, an average of about 0.08 km each, though that average describes no actual row. A new scheme in Italy would have to beat 0.08 km to change the head of this table, and that is the figure worth rechecking when one opens.

1 entries fall below a kilometre, short enough that portals and approaches usually decided their cost more than the bore itself. 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.

Reading the figures

5 of the 5 rows carry an entry in the notes column — 100 per cent of the table — and that column is where the qualifications live: tube counts, closures, boundaries and the reason a figure reads the way it does. Italian motorway inventories list tunnels and viaducts together in running order along the A08.

The longest entry is Olona, at 0.08 km. The note column records 17 exits, 10 motorway connections and 2 toll barriers along the route, in running order rather than by size. Water under pressure is the single most disruptive thing a heading can meet, and it is rarely where the survey said it would be.

The note column places the route in Lombardy, and the administrative area is recorded because a section is identified by it. The kilometre point is recorded for each structure on the A08, which is how the operator identifies it. Drill-and-blast remains normal in hard rock, and dominates the Scandinavian and Alpine entries in this record.

A crossing whose two carriageways differ in length is recorded once per direction rather than once per crossing. Tunnel building in Italy is shaped by geology and settlement pattern as much as by transport policy. Two-way traffic in a single bore is the arrangement every modern regulation tries to avoid and older crossings are full of.

Rock cover above a subsea bore is the governing design constraint, not the depth of the water itself. Rock temperature rises with depth, and on the deepest alpine crossings the working face has needed cooling before it needed lighting. Portals weather faster than the bore behind them, being the only part exposed to frost and sun.