Swiss company Cargo Sous Terrain plans to reform freight transport by going underground on a large scale. In the shadow of more flashy developments like the Teslas zipping under Las Vegas, they follow a more down-to-earth (literally) approach. Learn more about this new concept for freight transport in this article.

Connecting Swiss Cities Underground

The Swiss people have a knack for building underground. Record-breaking projects like the Gotthard Base Tunnel prove they are master tunnel builders. But now they aim to top these accomplishments by an even more ambitious project: The company Cargo Sous Terrain (CST) wants to build an underground transportation network that connects almost all major cities in Switzerland, from Geneva to St. Gallen. This would be more than 500km!

The network is connected to other transport modes like street and railway transport in hubs.
Trains of autonomous transport cars travel between the hubs.
In the hubs, the cars are lifted from the tunnel and are then unloaded to other vehicles.
Hubs could be located close to a city. Here they would become a base for fine-granular distribution with clean modes of transportation like cargo bikes.
The second kind of hub could be located in industrial areas, where they are close to the produces or consumers of goods.

Can It Work?

Building a 500km tunnel network in a densely settled country like Switzerland certainly sounds ambitious – both from a technical and an economical viewpoint. But how realistic are these plans? Let’s first have a look at the open technical questions, and afterwords look at it from a business perspective.

The first feat the engineers have to accomplish is to build the tunnels. Building such a long tunnel network is certainly a big challenge, but in principle it might be solvable unless there are underground conditions that prevent tunnelling in certain places. The company is trying to spot these problems early on by probing the conditions underground. Let’s assume these risks can be avoided and tunnel construction proceeds as planned. Then there are more technical challenges to come.

The cars need a propulsion system to travel underground. In the original plans, each car should travel autonomously with its own electric drive. In this solution, cars could navigate through the tunnels and eventually evade broken down cars (provided the tunnel’s width is sufficient). On the other hand, these vehicles would be more complex and thus more expensive. Also, each would need its own battery pack, which is a potential fire hazard.

For these reasons, the project just recently switched the approach to propulsion from autonomously driving cars to cars that are pulled by a cable, like a funicular. They claim this makes the whole system simpler, and they can rely on proven technology for cable-cars. Granted, there is a lot of experience with cable-cars in Switzerland, both with gondolas and funiculars. On the other hand, this could bring other problems. If all cars are driven by a cable, then they can no longer evade each other. If just one car breaks down, all other cars will be stuck. And how to move the cars around outside the tunnels? The company does not describe its new concept on their homepage yet.

Another drawback of cable-cars might be the speed. How fast can the cars travel? Existing ground based cable-cars like the famous San Francisco cable-car are rather slow, they go about 15kph. Can CST achieve a higher speed? If not, they will have a hard time competing with trucks, which can move at about 80kph on Swiss highways.

Is It Worth it?

If all these challenges can be solved, what will be gained by it?

The first question is about the capacity of the system. How can we estimate it?
Facts are hard to come by on the CST homepage.
If we look at this rendering, it appears the capacity of a single CST car should be about 2 Euro-pallets.

The capacity of a large 40 ton truck is 34 Euro-palettes. This means, to replace a single truck, a train of 17 cars needs to travel in the tunnels.

A Euro-palette has a size of 120cm x 80cm. Based on the picture above, we thus could estimate the length of the vehicle to be about 3 times 120cm (2 palettes plus overhead). This would give us 3.60m. A train of 17 cars would then have a length of 61.2m. Compared with a railroad, this is not a very long train. But we need to think about the infrastructure to move this trains up and down. The longer the trains, the longer the lifts need to be. And a lift of about 60m length will be mechanically rather complex.

Then for busy hubs, you would need multiple lifts in parallel, so that trains can move upwards and downwards in parallel. While trains wait for a free lift, they need to be in a parking position, so space for this is needed as well. It also needs a lot of switches. It appears that the space underneath the hubs will be some of the most complex parts of the system, limiting its capacity or driving the costs.

Let’s assume the trains can travel at about 30kph (not sure if this is realistic, see the comparison of other cable cars above). Then the braking distance on dry tracks would be about 26m (calculations done here). For simplicity I assume that the distance between trains in the tunnels should be twice this number, so 52m. In total, the total length that a train that replaces a single truck occupies 61 + 52 = 113 m. A 40t truck is about 18m long. Assuming trucks travel in about equal distance to their length (often they don’t), then the total length that is occupied is about 36m.

This clearly gives an advantage in capacity to trucks over the proposed CST system. It is unlikely that CST will completely replace trucks.

Yet there are other advantages to the tunnel system to consider here, even though the capacity might be lower.

One is that operation is autonomous. This reduces the need for truck drivers, which are in short supply. Also, the cars do not have to rest, increasing their overall speed somewhat.
In addition, the cars can travel regardless of weather conditions, making them more reliable in harsh winters – or even in wartime conditions.

Outlook

CST is a very interesting concept. The overall capacity might not be enough to replace trucks for good, but it could be a good way to soak up some of the predicted increase in freight traffic which the overground transport systems cannot handle any more.

It also has potential advantages in reliability and operating costs – if the company can solve the problem of trains getting stuck in the tunnel. A critical point will also be the capacity of the hubs, which are the mechanically most challenging parts.

The company also is very active, you can find many press reports on their homepage. The list of shareholders reads like the who-is-who of the Swiss economy, thus there is certainly some financial interest behind.

Yet with the project in its early stages, the many technical challenges that I describe and the long time horizon, it is too early to tell which fate CST will have. Will it end up like other predecessors of underground transportation like the London Pneumatic Despatch Company, or will it become another backbone of the Swiss economy? It is too early to tell, but most certainly a project to watch!