With more than six million kilometers of highways and 240,000 kilometers of railways snaking across the United States, life above ground has become increasingly congested. Tunnels provide some of the last available space for cars and trains, water and sewage, even power and communication lines. Today, it's safe to bore through mountains and burrow beneath oceans — but it was not always this way. In fact, it took engineers thousands of years to perfect the art of digging tunnels.
 

When England and France decided to link their two countries with a 32-mile rail tunnel beneath the English Channel, engineers were faced with a huge challenge. Not only would they have to build one of the longest tunnels in the world; they would have to convince the public that passengers would be safe in a tunnel this size. Tunnel fires, like the Holland Tunnel disaster, were common at this time. How did the engineers resolve this problem? They built an escape route.

The Channel Tunnel, also called the Euro Tunnel or Chunnel, actually consists of three tunnels, each 50 km long and bored in the rock below the seabed of the Channel. Two of the tubes are full sized and accommodate rail traffic. In between the two train tunnels is a smaller service tunnel that serves as an emergency escape route. There are also several "cross-over" passages that allow trains to switch from one track to another. Just one year after the Chunnel opened, this engineering design was put to the test. Thirty-one people were trapped in a fire that broke out in a train coming from France. The design worked. Everyone was able to escape through the service tunnel.

It took just three years for tunnel boring machines from France and England to chew through the chalky earth and meet hundreds of feet below the surface of the English Channel. Today, trains roar through the tunnel at speeds up to 100 miles per hour and it's possible to get from one end to the other in only 20 minutes!

Fast Facts

At the time it was being built, the Chunnel was the most expensive construction project ever conceived. It took $21 billion to complete the tunnel. That's 700 times more expensive than the cost to build the Golden Gate Bridge!

Many of the tunnel boring machines used on the Chunnel were as long as two football fields and capable of boring 250 feet a day.

When construction began in 1988, British and French tunnel workers raced to reach the middle of the tunnel first. The British won.

In the first five years of operation, trains carried 28 million passengers and 12 million tons of freight through the tunnel.

Vital Statistics

Location: Folkestone, England, and Sangatte, France
Completion Date: 1994
Cost: $21 billion (£9,000,000,000)
Overall Length: 163,680 feet / 50.45 km / 31.35 miles
Under Sea Length: 38 km / 24 miles
Purpose: Railway
Setting: Underwater
Materials: Steel, concrete
Engineer(s): Transmanche Link Engineering Firm