Why They Built The World’s Longest Rail Tunnel

Added: 2026-05-29

[00:00:00]The longest hot dog ever recorded is 336 feet or 102 m, which is frankly pathetic. That's only as much hot dog as I eat in like 3 days. I was going to write a video about the logistics of lengthening a hot dog to world record levels, but clearly there's nothing to say. That's why instead we're going to be talking about a different world's longest thing, the Gothard Base Tunnel, otherwise known as the longest rail tunnel in the world. Stretching from the small Swiss town of Ursfeld to the even smaller Swissier town of Bodio on the other side of the Alps, this thing puts the hot dog to shame. The question is, why did Twistland need to build the world's longest rail tunnel? And how do you even go about doing such a thing?

[00:00:38]Let's find out together. As I mentioned earlier, this rail tunnel cuts through here, the Swiss Alps. The Alps have never been transportation's best friend.

[00:00:46]For centuries, one of the only ways to get from tomato Europe to potato Europe was through the Gatard Pass. Trying to circumvent the Alps entirely requires doing something like this or this, which uh sucks. The Gothard Pass, though, is no cakewalk either. It's at 6,900 feet or 2100 m of elevation and full of snow for at least 7 months a year. By mule, crossing the pass took 7 days and killed you like half the time. Once they built the first road in 1830, that got cut down to 23 very unpleasant hours. Then Alfred Nobel, Mr. Priest Prize himself, invented dynamite. And in the 1880s they exploded their way from Aolo to Goshan.

[00:01:24]This tunnel was a major breakthrough literally allowing passenger and cargo trains to cross the Alps from Italy to Switzerland in just a few hours. Still, it had its limits. The original Gotchyard base tunnel sits at an elevation of 3600 ft or 1,100 m, which means that trains have to go up and down these spiraly doodads to get to the tunnel in the first place. This puts a pretty strict limit on how long and how heavy they can be, so moving cargo across the pass was still a problem.

[00:01:49]Over the years, more and more cargo started being carried by truck. And by the end of the 20th century, Switzerland's mountain roads had reached their limits. So, the Swiss did what you do when your roads get too congested.

[00:01:59]Keep adding lanes forever until your entire country is just one giant beautiful park. Oh. Oh, wait. No, sorry.

[00:02:05]No, that was the American Handbook of Infrastructure Excellence. No, in Europe, instead of adding more lanes, they simply dig the longest rail tunnel in the entire world. The theory was simple. If you dig a tunnel through the base of the mountain closer to sea level, you could run any train through it. Highspeed passenger rail and heavy cargo rail would finally be able to cross the Alps. The only problem is you would need to build the longest and most expensive rail tunnel ever built. It would cost Switzerland $12 billion and take more than a decade to complete.

[00:02:33]Surely this would be an incredibly divisive political f Oh no, never mind.

[00:02:37]The Swiss just voted to tax themselves $1,000 each so that they could start work on the tunnel immediately. I didn't know you could do that. Of course, securing the funding for the tunnel was only part of the problem. The real question was how you would actually go about digging the thing. The Gothur base tunnel, as it became known, would need to be 35 miles or 57 km cut straight through the base of a solid granite mountain. For safety reasons, you need two main tubes in case one catches on fire and 178 cross passages to serve as escape routes and maintenance access.

[00:03:05]You also need specialized ventilation systems to keep the tunnel cool. It would reach ambient temperatures of 115° F or 46 C otherwise and hundreds of miles of drainage pipes to stop the thing from constantly flooding with groundwater. It's a lot more than just a hole through a mountain. But even the hole is complicated. Digging the tunnel from one end to the other, or even from both ends to the middle, would take around 20 to 30 years. By then, we were all supposed to have jetpacks anyway, so that wasn't going to be an option.

[00:03:33]Instead, the tunnel's construction was divided into five sections that could all be excavated simultaneously, each with their own crews, base camps, cafeterias, and living facilities. This considerably sped things up, but required a stunning feat of logistics.

[00:03:47]All five sections of the tunnel needed to coordinate millimeter by millimeter to line things up perfectly. The margin for error across the entire tunnel was only 25 cm. Any more than that, and a stern Swiss man would probably shake his head disapprovingly. So, how did they do it? Well, step one is years and years of surveying, lasers, paperwork, and looking at rocks under a magnifying glass. But the tunnel itself started taking shape around 2003. Work began on the Bodio section of the southern end of the tunnel with just two ladies named and Heidi doing all the digging.

[00:04:17]They were able to pull off this incredible feat by channeling that classic German grit and ingenuity, and also by channeling the fact that they were not human ladies, but were in fact herneck gripper tunnel boring machines.

[00:04:28]These 3,000 ton beauties are specifically designed to deal with the kind of geology you encounter when you're German enough to drill straight into the middle of a solid mountain.

[00:04:36]Mostly nice and granite. All highdensity, high pressure crystalline rock. Conventional digging doesn't really work here. Granite has a really high compressive strength, meaning that it's almost impossible to crush with something like a pick or a shovel. Its real weakness is actually the opposite.

[00:04:50]It has a low tensile strength, meaning that it's easy to shatter or pull apart.

[00:04:54]Kind of like benifer. The Gripper TBM is designed to exploit this weakness by shoving a bunch of teeth into the face of the rock and twisting it with about 27 million ntons of force. At that pressure, the rock shatters and cleanly chips off into pieces, which are then collected along a conveyor belt and sent backwards out of the tunnel to be turned into whatever it is that German people eat. This is not exactly a quick process. The bodio section averaged around 45 to 52 feet or 14 to 16 m of progress a day and slowed down to just 3 to 6 ft or 1 to2 m around here in the calcarite zone where the rock got too soft for anything to get done. Insert Innuendo. When and Heidi were slowly trudging their way forward, work was already well underway to open up the middle of the mountain. For Pho and Amstag, this meant drilling dozens of access tunnels to get more workers and TBMs into the mountain. But for Cedrin, the middlemost section, the excavation process was entirely different. This was so deep in the mountain that the only access tunnel was less of a tunnel and more of a a hole. It was a 2700 ft 820 m vertical shaft dug straight into the earth. And not to body shame, but and Heidi were a little too voluuptuous to make it down in one piece. Getting a TBM down this hole wasn't going to be an option. But you know what? You can throw down a hole? A bunch of Swiss guys with explosives. This section, all five miles or 8.5 km, was excavated using drill and blast. What's drill and blast? I'm glad you asked. Drill and blast is a cutting edge EDM genre pioneered by a mysterious musical genius who's a dentist. Oh, sorry. You meant the excavation technique. Oh, well, basically they just drill holes and then blast them. Stupid question. The last section to begin excavation was Ursfelt in August of 2007. It was the shortest and simplest to dig, so they saved it for last as a treat. The two TBMs used to dig Amstag, Gabby 1 and Gabby 2, were reused here to open up the tunnel's northern portal. By 2009, the Gabbies had reached Amst, and a year later, and Heidi broke into Cedron. This was the final breakthrough, connecting the north portal to the south portal, 35 mi or 57 km away. In the end, the alignment deviation across the entire tunnel was 3 in or 8 cm horizontally and a whopping 0.4 4 in or 1 cm vertically, which is frankly embarrassing and why the Gothar base tunnel remains one of Switzerland's greatest national shames to this day.

[00:07:12]Anyway, if you live in the United States, you're no stranger to national shame. But instead of tunnels that are several centimeters of skew, we have the data broker industry. What's the data broker industry? I'm glad you asked.

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