Tunnels and Viaducts on the A28 Motorway in Italy, by Kilometre Point

• 16entries listed
• 1.14 kmlongest bore
• 3.55 kmtotal length

The record table

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

How this table is compiled

Between the longest and the tenth-longest the drop is 1.08 km, which is the part of the table that changes when a single scheme opens. Where one of these 16 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.

Lengths for Italy are recorded in metres which is how the operators publish them and why the shortest entry here reads as 20 m and not a rounded figure. The longest entry is 57.0 times the shortest and 13.5 times the median, which is the quickest measure of how uneven the table is.

15 entries fall below a kilometre, short enough that portals and approaches usually decided their cost more than the bore itself. Read down the direction conegliano column, the 17 values run from 20 to 3 367 with a midpoint at 109; the spread rather than the maximum is what says how uneven this set is.

This page records the structures catalogued along the A28 in Italy, in a tunnel almanac maintained at this address since the late 1990s. The captions name 11 distinct places and structures — Venezia, Giulia and Sesto among them — and those names are the index into the length tables where each is recorded with its own figure.

The route table lists 16 structures with a recorded length, giving both carriageways where the two bores differ. The material on this page is held in 3 captions rather than in running text, 27 words of it, each written against the image or row it belongs to by the compiler who put the page together.

Reading the figures

A new scheme in Italy would have to beat 1.14 km to change the head of this table, and that is the figure worth rechecking when one opens. The twelfth longest, viaduct at 0.06 km, sits close enough to its neighbours that which of them ranks higher depends on how each was measured.

The eighth longest is Rio Buion at 0.11 km, which is about where this record stops being about record holders and starts being about ordinary infrastructure. The ten longest average 0.33 km against 0.05 km for everything below them, and that ratio is the clearest thing this table says about the distribution.

Noncello at 0.65 km and San Giuseppe at 0.38 km follow it, and lengths are given per carriageway because the two bores of a dual route are rarely cut to the same length. Glacial till is loose, wet and unpredictable, and the Scandinavian entries that took longest were rarely the ones through granite.

The table on this page runs to 23 rows and records Viaduct, Direction Conegliano, Direction Portogruaro and Notes for each of them, which is the shape the original compiler chose rather than one imposed here. Adding a metre to the longest tunnel in the world costs what adding a kilometre to an average one does.

The shortest recorded entry is 0.02 km against 1.14 km at the top, a spread of 57x across the same table. Laid end to end the entries on this page would run 3.55 km, which is a number with no engineering meaning but a useful sense of the scale of what is catalogued.