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Comment by Invictus0 | Hacker News Reader

Why cant they put a swinging bar at the tunnel height some distance before the tunnel? The bar knocks the top of the truck and wakes up whoever is driving to the fact that the truck is too tall.

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At higher speeds, and with semitrailer-type vehicles, drivers don't notice the banging far behind them.[1] Much of the trouble at the Sydney Harbor Tunnel involves overloaded trucks with tarps on top. The truck may have taken the same route before, but become overheight due to the load. Thus, driver overconfidence.

[1] https://www.sciencedirect.com/science/article/pii/S235214651...

They don't work - well at least they aren't idiot-proof. See the comment above regarding the Montague Bridge in Melbourne, Australia. They have those height bars installed and we still routinely have trucks being peeled open.

I have no idea how you can be so distracted when driving that you fail to register when your truck is whacked by those height bars, but ... ¯\_(ツ)_/¯

They're not stupid, they're tired.

They've been driving day in day out on autopilot. Signs begin to blur after a while.

Probably shouldn’t be driving so ...

There is a long list of unhelpful "Probably" statement's that don't solve the problem.

No. Really. Driving while tired is considered to be as bad as driving under the influence. HGV drivers should really be seeing rigorous testing for this but - hurdur - freedom

Or a wedge barrier: https://eci-illinois.com/wedge-barrier-versus-medium-size-tr...

i think the point is to prevent damage to trucks, not to completely destroy them

For a major tunnel like this, you'd rather prevent damage / long-term obstruction of the tunnel.

A technology meant to kill suicide bombers might be a little much for that.

Well, you'll kill the occupants instead of just get them stuck.

Then why not just build a throwaway structure the same shape as the tunnel, some ways from the entrance, for people to crash into instead?

no the point is to prevent damage to road thus preventing a mini catastrophe like an underwater tunnel collapsing

Destroying the truck is indeed overkill though

In my professional engineering opinion, this is very badass.

I wonder how it would do with a heavier truck (test is 7.5 ton, legal load limits here are 40 ton).

This sounds like the perfect solution, a few swinging bars, thin enough not to knock something over but enough to make a loud banging noise.

Just like the ones at parking garage entrances...

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