That's a cute high-tech solution. A simpler one is to put a horizontal bar, the same height as the tunnel's ceiling, which will physically stop the truck before causing millions worth of damages. It's often done in France, sometimes with an early warning: a first arch with chains hanging to the maximal height. It makes a lot of noise on the truck's top, but won't destroy it.
You just need to remember that a small number of people are just not going to get it. Mostly truck drivers that are dead tired. That water screen does the trick because you're not expecting it. Signs, bumps, and noises are all common to highway driving.
In Boston a few months ago a coach bus had the top ripped off going under a 10ft bridge on a road that truck/bus traffic is banned from. The driver hit several low bars and signs and plowed onward until the bridge cut the top off. Several times a year this happens on Storrow Drive, despite all the warning devices as some drivers just can't be reached.
This. People don't even realize how important it is that people operating heavy machinery are well rested, and sometimes even put down appropriate regulations as just "worker's issues". Then you get a sleepy, bored guy on a highway, with neither awareness to spot dangerous situations, or willpower left to restrain from doing stupid things. It's a testament to how good they are at their jobs that they get to their destinations at all.
And that's why the EU every truck needs to be legally fitted with a Tachometer that measures every parameter of a vehicle, and a truck driver cannot legally drive for more than 8 hours (I think they can do 9 hours once per week, and they need a 24h break at least once per week as well) - after that, they need at least 8 hour break, when the vehicle cannot move. If the truck is stopped by the police,and they find that the driver has been driving over the time limit in the past 3 months, they will issue a massive, multi-thousand euro fine, so it's extremely rare for drivers to work overtime.
I knew a driver who drove for loading at a company, and because it was taking them too long, his time for a break started before they finished. He refused to move the truck from the spot for a whole 8 hours,even though it was blocking the warehouse - he knew that if he moved it even a little bit, he(and the company he worked for) could be fined several thousand euros months down the line.
Actually I'm from EU country(-ie, actually), and it works... inconsistently. There's fraud, and there's shifting the blame on drivers while trying pressuring them to take the risks anyway (works especially 'well' in countries where many truck drivers are self-employed, like, say, Poland).
And then you get a Polish bus driver with a bus full of people going for a pilgrimage through Swiss Alps, which then fills the news for a week in two countries.
It's way better than nothing, though, and the deficiencies are something that should be fixed even within existing law (e.g. the "self-employment" could really easily be proved to be actually a normal job, if the prosecution cared enough).
I wonder if it would help to put some sort of heart rate monitor or something on the drivers, some way to detect that they are bone tired and require the companies to let them sleep.
That's the beauty of the metal bar 10m before the tunnel: they won't fail to notice when it acts as a can opener on their truck's cabin, and it only costs a metal bar in public infrastructure (plus towing a cabriolet truck out of the way)
A similar solution is used in my area yet perplexingly it still doesn't seem to stop it happening... so I think new ideas like this are definitely a good thing.
Did you see the truck in the video take out an enormous steel beam that was presumably attached to the structure of the tunnel in some kind of permanent way? How would your solution avoid the same fate?
The warning beam is several stopping-distances before the tunnel itself, and far easier to replace/reconstruct.
I'd try a 3-stage contact-warning system:
(1) hanging bar that makes noise on contact but causes little damage. This might even go before a suitable turn-off.
(2) breakaway cord with trailing noisemakers. This would be torn from its mast by the collision, and drag noisy items behind, emphasizing the need to stop and investigate.
(3) hard bar providing some slowing/resistance (but almost certainly not full stopping power, given the position and expense). By design this would actually damage the vehicle (and even risk harming the driver), approaching the same level of damage that would occur at functional tunnel-entry. But, it'd happen earlier where easier to clear/repair.
Oh, I like the water-wall too. But a driver who misses the 1st two no-damage physical-contact warnings I've proposed -- and thus would hit the damaging third hard bar -- would quite possibly ignore the water-wall too.
After all, the water wall seems primarily visual, and the driver has already missed numerous visual warnings. The contact protectors add collision-noise and vibration, which are rare enough that even a dozing/road-hypnotized driver is likely to take note.
That beam they took out is called a "sacrificial beam." It was not a structural support, but was meant to take the impact before any structural members were damaged. You'll see them on many modern bridges and underpasses.
That's interesting and seems like a good idea, except perhaps it should be paramount that the 20-ton beam NOT fall on the following cars! That is an entirely different meaning of "sacrificial"...
Solid beam is probably a bad idea, but many tunnels have chains dangling above the road at the tunnel's maximum height - if you hit them, you will hear it,but they will do little damage to the vehicle.
Solid beam is an excellent idea as last recourse, from a structural POV since the vehicle is going to be destroyed anyway it's better to destroy it before it damages the tunnel itself.
Excellent plan! A trapdoor! In the harbour tunnel!
Relevant anecdote: My Dad worked for the company who built the fire control system in the Sydney Harbour Tunnel. It's got (from fuzzy memory - numbers not guaranteed accurate) 128 sectors of "deluge valves". It's got pumps capable of keeping up with only 10 of those sectors of deluge valves - more than 10 sectors of valves open means even with all pumps running at maximum capacity the tunnel will fill up with water. There's some software controlling it all which is intended to ensure the operators don't accidentally flood the tunnel. Dad knows who wrote that software - he won't drive through the tunnel.
I guess they are afraid that the broken bar can damage some other vehicle. Still, something heavier that can be damaged and can stop the truck before the tunnel is the proper solution, not the strange projections. Drivers are too sleepy sometimes, in spite of the expectations of the idealists.
They showed footage where low bars did physically stop the truck (or at least tore off the top part of the cargo container), but this still caused debris to be showered across the tunnel entrance, which resulted in large traffic delays.
These will make a fair mess of a vehicle, I saw them hitting a lorry once but are pretty attention grabbing.
The Blackwall Tunnel has different heights and widths for different lanes due to the tunnel profile which is why the restrictions are different in each lane in this photo.
In some jurisdictions, the owner of the truck can sue you for damages if the structure was constructed with the intent and purpose of damaging the truck.
Yes, but that would require that the road close for debris to be picked up. The water wall solution allows the tunnel to resume operation quickly. A small jam in the Sydney Harbour Tunnel blocks the whole city, so we want to avoid unnecessarily large delays.
