Brenner Base Tunnel: length, alignment and expected opening date

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The record table

Figures as published by the promoter. The Brenner is a base tunnel: it exists to replace a climb over a pass with a level alignment beneath it, which is why it is long rather than high.

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

How this table is compiled

Comparing one country's practice against a neighbour's is more informative than reading either alone. Cost figures are excluded for a harder reason: currency, inflation and differing project scope make them close to meaningless in comparison. Where a structure belongs to two classes it appears on both tables, which is not double counting but two different measurements.

The Brenner Base Tunnel is being driven beneath the Brenner Pass between Austria and Italy. At 55 km it will be among the two or three longest railway tunnels in the world when it opens. That lower tunnel was driven first, which is standard practice: it de-risks the geology and later serves drainage and access.

Twin-tube crossings frequently show two slightly different lengths, because the two carriageways rarely follow the same line through the rock. This archive has recorded tunnel data since the late 1990s, compiled from operator publications, national administrations and the engineering press. Cross-passage spacing, fixed firefighting and emergency ventilation control are what modern safety regulation actually governs.

The arrangement is two single-track tubes with a service and exploratory tunnel running below and between them. A base tunnel trades a much greater length for a far lower summit altitude and a gentler ruling gradient. Subaqueous tunnels are governed by rock cover above the bore rather than by the depth of water above that.

Its published opening year is 2032, and like every scheme of this size that figure has moved before. Figures are checked against one another where sources disagree, and the disagreement is recorded rather than resolved silently. Tunnel engineering is a field where the qualifications attached to a number matter more than the number itself.

Reading the figures

Rows are ordered so that the head of the table answers the question most readers arrive with. Gradient limits are the main reason railway tunnels run longer than road tunnels on the same crossing. Reading the qualification before the figure is usually the faster route to understanding what a claim actually says.

The corridor it serves runs from Munich to Verona, and is the busiest Alpine freight crossing. Traffic figures are excluded throughout this archive, because they date far faster than the structures themselves. Under-construction works cannot hold a record. The archive grew through correspondence with engineers and administrations in more than twenty countries, and still does.

The note column is worth reading before the number. Every figure here is traceable to a named source. Dates use the day, month and year the event occurred. Ground conditions belong with every advance rate. A contained fire is more instructive than an uncontained one. The table is short because the sourcing bar is high.

Minor incidents are listed alongside the serious ones. Disputed values carry the dispute in the note column. Opening year means the year traffic was admitted. Two independent sources were required for each row. Promoter figures are used where no independent one exists. The date of verification is published with the table.

Height is measured above mean sea level. Nothing below is interpolated or rounded up. Segmental linings are erected behind the shield. Forecast dates are forecasts, and they move. Forecasts on schemes this size move by years. Deaths are the figures established by official inquiry. Secondary summaries were not used as a source.