Question 1

What is the longest tunnel in the world?

Accepted Answer

The Delaware Aqueduct, a water tunnel supplying New York City, holds the overall record at 137 km. The longest rail tunnel is the Gotthard Base Tunnel in Switzerland at 57.1 km, and the longest road tunnel is the Laerdal Tunnel in Norway at 24.5 km.

Question 2

What is the longest undersea tunnel?

Accepted Answer

The Seikan Tunnel in Japan, at 53.9 km with 23.3 km beneath the seabed, is the longest undersea tunnel. The Channel Tunnel follows closely. For road traffic the Ryfylke Tunnel in Norway is the longest fully undersea road tunnel at 14.3 km.

Question 3

Why are so many long tunnels in Norway?

Accepted Answer

Norway is cut by deep fjords and mountains, so boring underneath often beats ferries and pass roads on cost and reliability. The state finances subsea tunnels with tolls that are removed once loans are repaid, and the country now operates dozens of such links.

Question 4

How deep do undersea tunnels go?

Accepted Answer

The deepest undersea road tunnel, the Ryfylke Tunnel, reaches 292 m below sea level, while the Eiksund Tunnel sits at 287 m. Rail tunnels usually stay shallower in rock cover terms but the Seikan Tunnel passes 240 m beneath the seabed.

Question 5

Are long road tunnels safe in fires?

Accepted Answer

Modern tunnels are far safer than in the past. After the Mont Blanc fire of 1999 killed 39 people, operators added escape tubes, fire refuges, smoke extraction, spacing rules for trucks and radio systems. Fatal tunnel fires have become rare since these reforms.

Question 6

What was the first tunnel under a river?

Accepted Answer

The Thames Tunnel in London, opened in 1843, was the first tunnel bored successfully under a navigable river. Earlier attempts under the Thames failed. It was built by Marc and Isambard Kingdom Brunel and now carries the London Overground.

Water Tunnels: The Hidden Giants