A 91-ton steel shield was moved overnight into an Italian highway tunnel damaged by fire, the old concrete roof is being torn out and poured again right above it, and the cars and trucks keep driving through the middle the whole time, as long as they stand under 14 feet tall

Fixing an old highway tunnel usually means closing it. The road operator shuts a bore, puts up a forest of orange signs, sends everyone the long way around, and drivers spend a few months grumbling about the detour. I’ve sat in enough New York tunnel traffic to know that’s not a fun way to spend an afternoon.

But on Italy’s Adriatic coast, the company that runs the A14 highway is trying something different. Instead of shutting the Vinci tunnel between Pedaso and Grottammare, it’s parked a steel shield inside the southbound bore and is rebuilding the roof above it while cars and trucks keep driving through.

The shield weighs about 91 tons and it’s 29.5 feet long. Autostrade per l’Italia, which operates that stretch of road, said on October 17 that the shield would be moved into place that night and would be up and running from Monday, October 19. The company says it was custom-made for this tunnel’s shape, and that this is the first time it’s put one to work anywhere on the A14.

So what is this shield, exactly?

Autostrade calls it “a sort of small metal tunnel installed inside the tunnel” (that’s my translation from the Italian), and frankly that’s the best way to picture it. It’s a tunnel within a tunnel. The shield walls off the work zone from the traffic, and the road keeps running through the middle of it.

What’s being replaced is the vault. If you’re not up on tunnel jargon, that’s the curved roof over your head, and in this tunnel it’s a concrete lining. According to The Tunnelling Journal, the job involves stripping out the old lining up top, installing fresh waterproofing, adding steel rebar, and then casting a new concrete lining. Autostrade says the shield also helps with pouring the concrete for the new vault.

The shield doesn’t stay put, either. Autostrade says it’ll move forward progressively as the work goes on. So instead of one big closure, you basically get a job site that slowly travels down the tunnel. It’s a pretty clever way to do it.

There are a couple of things I can’t tell you, though. Autostrade hasn’t said how many lanes run through the shield during the day, or how far it moves each time it shifts forward. I couldn’t find either detail in The Tunnelling Journal’s write-up, so I won’t pretend to know.

If this sounds familiar, we’ve covered a couple of jobs like it. Deutsche Bahn used a 298-ton machine called Tilly to widen a rail tunnel while trains kept running through a steel tube inside it. And in south London, a drill rig pushed a hole under a live railroad without stopping the trains. Those were rail jobs. This one has cars and semis rolling through the middle, which I’d argue is a slightly more nerve-racking setup for everyone involved.

The Vinci tunnel was damaged in a fire

So why this tunnel in particular?

According to a decree from the Marche regional government issued in September 2025, the southbound bore of the Vinci tunnel was hit by a fire on April 4, 2024. The approved project covers rebuilding the tunnel’s permanent lining and restoring its systems. That decree also puts the tunnel at about 1,330 feet long, which is roughly a quarter of a mile.

The Vinci job also fits into a much bigger program. Autostrade’s tunnel plan covers 595 tunnel bores across its network, and its long-term renovations are designed for a nominal life of 50 years. If that holds up, the new vault should, in theory, be good for about half a century.

So what happens if your truck is too tall?

A steel tunnel inside a concrete tunnel has one obvious weak spot. Anything that doesn’t fit is going to have a very bad day.

The height limit through the work zone is just over 14 feet. Movyon, the Autostrade group’s technology company, has installed gantries ahead of the tunnel that check vehicle heights, and anything over the limit triggers a traffic light. Teams on site then stop the driver and send them to the Piceno Ovest service area, where Italy’s State Police check the vehicle.

It’s basically the same idea as the overheight warnings you’ll see in front of some older tunnels and low bridges in the US. Except here, there’s someone waiting to pull you aside. I’d imagine the conversation at Piceno Ovest is a pretty awkward one, but it beats wedging a box truck into a 91-ton steel tube.

Night work means sharing the other side

The shield doesn’t solve everything. At night, and during any work that can’t be done with traffic going past, Autostrade switches to a contraflow. That basically means southbound drivers get moved over to the northbound side of the highway, which heads toward Ancona, and both directions share it with one lane each.

There’s some flexibility built in, too. If traffic gets heavy or there’s an emergency, the company says it can stop work and temporarily open an extra lane.

Then there are the holiday breaks. Autostrade scheduled a pause from 6 a.m. on Friday, October 30, to 10 p.m. on Monday, November 2, for the All Saints’ Day weekend, with the shield coming out to give drivers back two lanes in each direction. The company says it’ll suspend the work over Christmas as well.

As for when the whole thing wraps up, I honestly don’t know. The Tunnelling Journal reports that the wider program has been described as running until the end of May 2027, but Autostrade didn’t confirm that date in its latest announcement.

The next pause is already on the calendar, though. Autostrade says work will stop again from 6 a.m. local time on Thursday, December 3, until 10 p.m. on Wednesday, December 9, and the 91-ton shield will be pulled out of the Vinci tunnel so traffic gets two lanes in each direction for that week.

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