The longest tunnels in North America: the record in each country

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The record table

Every North America country in this archive with a recorded tunnel, longest first. Structures not yet open to traffic are excluded, so a country's entry can be shorter than its best-known project.

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

How this table is compiled

Canada heads this table, with Detroit 1.56 km as its longest recorded structure. Published lengths for the same structure often differ by a few metres between sources, depending on whether the cut-and-cover approach is counted. A record of this kind moves whenever one scheme opens, and a page that is not re-checked drifts out of date silently.

Reading down the table shows how unevenly tunnelling is distributed even within one continent. The same journey time can be bought with one long bore in one country and a dozen short ones in another. Where a country has been redrawn administratively since an entry was recorded, the region code reflects the classification then in use.

Terrain explains most of that unevenness: a country with mountains and fjords will out-tunnel a flat neighbour many times over. Funding practice explains the rest, because tunnels arrive in waves once a network plan is approved. Country inventories in this archive are deeper than the summary row suggests, often running to a hundred entries or more.

Geology and settlement pattern shape a national list far more than transport policy does. Cross-border tunnels are recorded under both countries, so the Channel Tunnel appears for France and for the United Kingdom alike. Nothing on this page is estimated: a value that could not be corroborated is left blank rather than filled in.

Comparing a national list against a neighbour's is more informative than reading either alone. Twin-tube crossings frequently carry two slightly different lengths, because the two carriageways rarely follow the same line through the rock. Opening dates refer to the admission of traffic rather than to breakthrough, which normally falls a year or two earlier.

Reading the figures

The table covers 3 countries, each linking through to an inventory that usually runs far deeper than one row. Continental rollups are the view this archive has never published, and they are derived from the same per-country inventories. Gradient limits are the main reason a country's longest railway tunnel usually exceeds its longest road tunnel.

This archive has held per-country tunnel inventories since the late 1990s, and this page is the aggregation across them. Subaqueous tunnels are governed by rock cover above the bore rather than by the depth of water above that. Figures are compiled from operator publications, national administrations and the engineering press, and checked against one another.

Toll arrangements and traffic figures are excluded throughout, because both change far faster than the structures do. Where a country's best-known project is still under construction, its entry here is the longest structure actually carrying traffic. Ventilation shafts allow a longer bore to be driven, and their absence is often what caps a national record.

Cross-border tunnels appear under both countries. Length is measured portal to portal. Opening year means the year traffic was admitted. Metres and kilometres follow the source publication. Two sources were required for every figure. Rail figures follow the track centre line. Names follow the operator's own spelling. A country's entry links to its full inventory.