Designing highways that cross mountain ranges or water obstacles requires more than 20 kilometers of underground sections, turning ordinary trips into unique engineering challenges. Modern car tunnels They are complex life support systems, where each kilometer of length dictates its own strict requirements for ventilation, lighting and fire safety. The depth of occurrence and geological conditions often determine not only the cost, but also the very possibility of creating a through passage for freight and passenger transport.
Engineers must take into account the enormous pressure of rocks and the risk of groundwater breakthrough, which makes the construction of such projects one of the most dangerous activities in peacetime. Monitoring systems monitor the slightest deformation of the arch 24 hours a day, transmitting data to the central control center. An error in calculations during excavation can cost billions of dollars in losses and human lives, so a multiple safety margin is built in.
The construction of such facilities takes decades, and their operation requires constant attention and expensive infrastructure maintenance.
Leaders of the planet's underground highways
The undisputed leader for many years has been La Ranche in Norway, whose length is 24.51 kilometers. This one double-pipe tunnel was opened relatively recently and became part of the important transport corridor E39 connecting the western coast of Scandinavia. A special feature of the project was the need to lay the route under a deep fjord, where the sea depth reaches almost 400 meters.
To ensure safety along such a length, special emergency niches and turning points were provided every few hundred meters.
The second place is confidently held by the Swiss Gotthard Base Tunnel, although its main function is railway; in parallel, there are also road arteries, which are only slightly inferior to the leaders. However, if we talk specifically about purely automobile crossings, then the list is headed by objects located in hard-to-reach areas. Horizontal penetration in such conditions, it was carried out on both sides of the mountain, and the engineers had to join the two faces with millimeter precision.
⚠️ Attention: Driving through the longest tunnels in the world often limits the height of vehicles and requires that headlights be turned on.
Statistics show that with the commissioning of new giants, the average speed of routes has increased significantly. Previously, drivers had to make a huge detour through mountain passes, which was almost impossible in winter due to snow drifts. Now transport accessibility regions has improved, but the responsibility of drivers for complying with the speed limit in a confined space has also increased.
- 🚗La Ranche (Norway) - 24.51 km
- 🚙 Shennongjia (China) - 28.3 km (design/construction)
- 🚕 Saint Gotthard (Switzerland) - 16.94 km
- 🚓 Arlberg (Austria) - 13.97 km
- 🚙 Mont Blanc (France/Italy) - 11.6 km
Technical features and security systems
A key element of any extended underground structure is a forced ventilation system. In tunnels longer than 10 kilometers, natural draft does not work, so powerful ventilation shafts and jet fans located under the ceiling. They not only supply fresh air, but also remove exhaust gases, the concentration of which can become critical during heavy traffic.
In the event of a fire, the ventilation system switches to emergency mode, creating an air flow that drives smoke away from people and allows them to evacuate to a safe area.
Lighting in such objects is divided into several zones: entrance, intermediate and exit. The driver's eyes must adapt to changes in brightness, so high-power lamps are installed at the entrance to simulate daylight. LED matrices allow you to instantly change lighting scenarios, indicating closed lanes or detour directions in the event of an accident.
Automated incident detection systems scan the video stream in real time, identifying stopped vehicles or smoke. Once the algorithm detects an anomaly, alarm automatically sends coordinates to the dispatcher and changes traffic lights at the entrance, blocking traffic.
⚠️ Attention: It is prohibited to transport dangerous goods in long tunnels without special permission and escort.
Difficulties of construction in mountainous conditions
Tunneling in the highlands carries the risk of sudden releases of gas and thermal waters. Geologists conduct a thorough analysis of the rock before starting work, but nature often makes its own adjustments. Usage tunnel boring complexes (TPK) allows you to drill and at the same time strengthen the vault with concrete rings, which speeds up the process and reduces the risk of collapse.
The temperature inside the mountain at great depths can reach 40-50 degrees Celsius, which requires the installation of powerful cooling systems for the operation of equipment and people.
The logistics of soil removal also poses a separate challenge. Temporary railway lines or conveyor belts are built to remove millions of cubic meters of rock. Environmental control requires that the recovered materials be disposed of without harming the environment; they are often processed into crushed stone for construction.
Interesting fact about technology
Some tunnels use robotic inspectors that autonomously move along the ceiling and check the condition of the lining slabs for cracks.>
Economic impact on regions
The appearance of an extra-long tunnel radically changes the economy of the surrounding areas. Reducing travel time makes commuting and delivery of perishable goods possible. Logistics centers begin to grow around portals, creating new jobs and developing service infrastructure.
The tourist flow is also increasing, as previously inaccessible areas become reachable all year round, regardless of the weather.
However, the maintenance of such facilities places a heavy burden on the budget. Repairing the roadway, replacing equipment and paying for electricity for ventilation require constant infusions. Often, to compensate for expenses, paid tariffs, which may cause dissatisfaction among local residents, but is a necessity.
Comparison table of characteristics
For clarity, we present data on the main parameters of the rating leaders in order to assess the scale of engineering solutions.
| Title | Country | Length (km) | Opening year | Feature |
|---|---|---|---|---|
| La Ranche | Norway | 24,51 | 2023 | Underwater section |
| Shennongjia | China | 28,30 | 2022 | mountain range |
| Saint Gotthard | Switzerland | 16,94 | 1980 | High traffic |
| Arlberg | Austria | 13,97 | 1978 | Alpine transit |
| Frejus | France/Italy | 12,87 | 1980 | EU border |
Rules of conduct and recommendations for drivers
When entering a long tunnel, you must take off your sunglasses and turn on your headlights on low beam, even if it is bright there. The distance to the car in front should be increased, since in a confined space the perception of speed and distance is distorted. Prohibited stop unless absolutely necessary, turn around and exceed the speed limit.
In the event of a breakdown, you should drive to the nearest emergency niche, which are located at certain intervals and marked with light signs.
Listen to radio messages on the specified frequency; they broadcast operational data about the situation on the route. If it catches fire alarm in the tunnel, immediately follow the instructions on the board and the instructions of the security personnel.
☑️ Checklist before entering a long tunnel
Prospects for the development of underground infrastructure
In the future, we will see the emergence of even more extensive facilities, including combined ones, where automobile levels will be combined with railway ones. Technologies 3D modeling and artificial intelligence make it possible to design routes with minimal impact on the landscape.
Development of fully automated tunnels is underway, where traffic movement will be coordinated by a central computer without human intervention.
The main trend of the coming decades is to improve the environmental friendliness and energy efficiency of underground passages. Solar panels on portals and energy recovery from ventilation will become standard for new projects.Tip: Always keep a tunnel map or a saved photo of the evacuation diagram in your glove compartment if you plan on frequent trips through a particular difficult section.
Why do they change the lighting in tunnels?
Changing the brightness and color temperature of the light helps the driver's eyes adapt when entering and exiting, reducing the risk of blindness and increasing concentration.
What to do if the engine stalls in the tunnel?
It is necessary to turn on the hazard warning lights, put up a sign (if it is safe to do so), leave the vehicle and proceed to the nearest emergency exit or telephone.
How often are security systems checked?
Testing of fans, pumps and fire suppression systems is carried out regularly, often weekly or monthly, with full-scale drills conducted once a year.
Is it possible to reverse in the tunnel?
Strictly prohibited. Reversing in a tunnel is a gross violation of the rules and creates a deadly situation for other road users.