The Chunnel, deep inside and behind the scenes (photos)

CALAIS, France--For many Americans, the idea of taking the train from England to France, or vice versa, means one thing: the Eurostar. But actually, Eurostar is just one customer of a much larger operation: the Eurotunnel, otherwise known as the Chunnel.

Since the 31-mile-long tunnel opened in 1994, more than 265 million passengers, and more than 53 million vehicles--including 16 million heavy goods vehicles--have traveled across its tracks.

Each day, 50 Eurostar trains take passengers between London and either Paris or Brussels, but that's just a fraction of the 450 trains a day that pass through the tunnel carrying trucks, containers, cars, buses, and more. And because it takes trains just 35 minutes to go between the Continent and England, the tunnel has become serious competition for the ferries that used to dominate such transportation.

While the Eurostar is by far the most well-known customer of the Eurotunnel, many companies are customers of the Paris-based organization that runs the tunnel. And it also runs its own trains, selling space to passenger cars, trucks, buses, and other vehicles.

Here, we see one of Eurotunnel's own locomotives emerging from the tunnel, a view that is not available to the public. CNET got a special look behind the scenes as part of Road Trip 2011.

As part of Road Trip 2011, CNET got a ride in the cab of a passenger vehicle train heading through the Eurotunnel. Here, we see the entrance to the tunnel--actually, both tunnels, including the one that carries trains from north to south, and the other, through which trains go south to north, just before entering from the France side.

This is Eurotunnel train driver Tracy, smiling as she makes her way deep into the darkness of the 31-mile-long tunnel between France and England.

Eurotunnel train drivers have their maximum speed dictated by operators in the railway control center, either on the UK side of the tunnel or the France side. Generally, non-Eurostar trains have a maximum speed of 140 kilometers--87 miles--an hour. Eurostar trains are allowed to travel up to 160 kilometers--99 miles--an hour. Here, we see that Tracy's train is going 138 kilometers--86 miles--an hour.

At the Eurotunnel's railway control center (RCC), operators can monitor every train that goes through either of the two tunnels that travel between England and France on the largest real-time optical control board in the world. Here, we see the entire board, known as the TCO, in the RCC on the UK side of the tunnel. There is a second RCC on the France side with an identical TCO.

This is the optical real-time control board that allows operators in the Eurotunnel's railway control center to monitor all train traffic through the side-by-side tunnels between France and England. On this side of the board, we see the section that corresponds with the giant Calais, France-based terminal from which huge numbers of trains carrying everything from passenger cars to buses to cargo trucks depart each day. Each of the main green lines represents a track and the 4- or 5-digit numbers correspond to a specific train. If the number begins with a "7" it means it's a train carrying trucks and cargo. The all-digital board updates in real-time.

In the middle left of this image, we see a yellow line with the number "7365." This corresponds to the length of a truck-carrying train that is heading from France to the UK.

This is a computer-based graph that shows the progress of any train in either of the two tunnels in space and time. The train's time of departure is on the X axis, and its place in the tunnel--designated by a code--is on the Y axis.

Here we see the two tunnels--on the France side--with no trains passing through. Moments later, a truck train emerges having just completed the journey from England.

Having just emerged from the tunnel, this train is carrying trucks and other heavy equipment.

This illustration shows the configuration of the Eurotunnel--its two main tunnels, as well as its service tunnel, ventilation system, and cross passages.

This is a Eurotunnel photograph of the interior of one of the tunnels.

Here, we see two Eurotunnel employees, including Jean-Luc Pochet (left), the manager of the service tunnel infrastructure, walking into the service tunnel from the France side. The service tunnel allows maintenance and other official vehicles to drive through, as well as being the escape route passengers would enter if there was an emergency in either of the train tunnels. An overpressure system built into the infrastructure is designed to pull smoke out of the main tunnels, allowing passengers to escape a fire without the danger of smoke inhalation.

Here, we see one of the fire doors that are located throughout the service tunnel closing. The doors are designed to isolate a fire if one should break out, as well as to maintain the proper pressure in the tunnels.

This is a view of the Eurotunnel service tunnel.

Eurotunnel maintains a fleet of 57 locomotives and more than 900 wagons. The company is in the process of upgrading many of the locomotives from 5.6 megawatts to 7 megawatts because of increased passenger and freight traffic through the tunnels between France and the UK. It is also being done in anticipation of further increases in traffic due to the London Olympics being held in 2012.

This is one of the shuttle vehicles that ferry people through the service tunnel. The vehicles drive along a magnetic line that keeps them on a straight line inside the tunnel. Otherwise, drivers would have trouble staying on a straight line.

Part of the upgrading process for the locomotives involves replacing the complex equipment underneath the train, including air conditioning, ventilation, and more. These systems are entirely unique to Eurotunnel's trains, and are said by the company to be among the most sophisticated installed on any trains anywhere in the world. Here we see one of the locomotives lifted up for its retrofit.

This is a fire door in one of the passageways between the two main tunnels. On the lower left of the door, you can also see hose fittings for fire crews from both the UK and France. This is so the first crew that arrives, whichever country they come from, can attach their hoses--which are different in each country.

This is a look into an empty Eurotunnel passenger car wagon. Each wagon can hold several cars, and during the ride between the Continent and the UK, passengers can get out of the cars and relax in comfort. The wagons can hold buses, RVs, cars, and other passenger vehicles, even those that are taller than normal cars.

Here we see a bus emerging from one of the passenger vehicle wagons on the UK side of the Chunnel.

Eurotunnel maintains what it says is the largest train maintenance shop in Europe. While much of the work that goes on there is done on individual locomotives or wagons, there is a section of the shop that is long enough to hold entire trains, such as the two seen here.

Just outside of the maintenance shop, we see many train axles lined up for various purposes.

Here, we see a close-up view of the interior of one of the passenger-car wagons.

Here we see a train chassis that is being retrofitted. This is at the Eurotunnel maintenance shop in Calais, France.

Here we see a train axle being lifted by a crane and being carried to where it will be worked on or re-attached to a train wagon or locomotive.

Here we see a Eurotunnel wagon lifted off the ground so that crews can work on the complex equipment located underneath.

This is a new wheel attached to a train axle at the Eurotunnel maintenance shop in Calais, France.

This is one of two gigantic shafts at either end of the Eurotunnel that houses piping for ventilation, water for firefighting, and cooling. The equipment is located at the top of the shafts, which on the France side is about 3 kilometers north of the entrance to the tunnel. The shaft is 187 feet wide, and 131 feet tall, big enough, it is said, to fit the entire Arc de Triomphe.

This is an Airedale that is in the back of a car on a Eurotunnel passenger-car wagon. Passengers are able to carry pets back and forth between France and the UK, so long as they acquire a "passport" for their animal.