Rogfast: the deepest and longest subsea road tunnel in Norway

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The record table

On a subsea tunnel the governing constraint is rock cover above the bore, not the depth of the water. Rogfast will take both the length and the depth records in this class when it opens.

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

How this table is compiled

Too little cover and the bore risks connecting to the seabed; too much and the tunnel becomes needlessly long and steep. Corrections have historically arrived by letter rather than by form, and that is still how most errors in it have been found. Where a figure could not be corroborated it was left out.

The scheme includes an interchange constructed beneath the fjord, serving the island of Kvitsoy. Where a structure belongs to two classes it appears on both tables, which is not double counting but two different measurements. Cost figures are excluded for a harder reason: currency, inflation and differing project scope make them close to meaningless in comparison.

Rogfast is being driven under the Boknafjord north of Stavanger, on the E39 coastal route. Norway builds this class of tunnel to replace ferry links, and the economics are calculated against the ferry it removes. Twin-tube crossings frequently show two slightly different lengths, because the two carriageways rarely follow the same line through the rock.

Traffic figures are excluded throughout this archive, because they date far faster than the structures themselves. Subaqueous tunnels are governed by rock cover above the bore rather than by the depth of water above that. This archive has recorded tunnel data since the late 1990s, compiled from operator publications, national administrations and the engineering press.

Tunnel engineering is a field where the qualifications attached to a number matter more than the number itself. Figures are checked against one another where sources disagree, and the disagreement is recorded rather than resolved silently. A base tunnel trades a much greater length for a far lower summit altitude and a gentler ruling gradient.

Reading the figures

Both records are currently held by Ryfylke, a few kilometres away and less than half as deep. Rows are ordered so that the head of the table answers the question most readers arrive with. Reading the qualification before the figure is usually the faster route to understanding what a claim actually says.

Under-construction works cannot hold a record. Cross-passage spacing, fixed firefighting and emergency ventilation control are what modern safety regulation actually governs. Gradient limits are the main reason railway tunnels run longer than road tunnels on the same crossing. The archive grew through correspondence with engineers and administrations in more than twenty countries, and still does.

Dates use the day, month and year the event occurred. The note column is worth reading before the number. Comparing one country's practice against a neighbour's is more informative than reading either alone. Promoter figures are used where no independent one exists. A contained fire is more instructive than an uncontained one.

Minor incidents are listed alongside the serious ones. Opening year means the year traffic was admitted. Metres are used for structures, kilometres for routes. Every figure here is traceable to a named source. The date of verification is published with the table. Disputed values carry the dispute in the note column.

Ground conditions belong with every advance rate. Spoil is removed back through the machine. Segmental linings are erected behind the shield. Secondary summaries were not used as a source. Forecasts on schemes this size move by years. Deaths are the figures established by official inquiry. Forecast dates are forecasts, and they move.