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11 Foot 8 – The Can-opener Bridge

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Re: 11 Foot 8 – The Can-opener Bridge

#111

Post by teraflop »

LegitShady wrote: post #104
teraflop wrote: post #9

Earlier quoted context omitted.

Placing an obstacle between the bridge and the intersection would be fairly pointless, because once you hit it, it would be too late to stop before hitting the bridge. (EDIT: in addition, a hanging warning sign would have to be suspended from something. My guess is any such structure would need to be made very sturdy and expensive, or else it would just get knocked down and increase the hazard to pedestrians and prop…

Look at the video. Such a structure already exists. There is a yellow beam meant to protect the bridge right in front of it. It probably does most of the can openjng to spare the bridge

The parent commenter asked for something that would "impact but not damage" vehicles, and the protective beam undoubtedly fails at that purpose.

Re: 11 Foot 8 – The Can-opener Bridge

#112

Post by hwc »

quickthrower2 wrote: post #103

For the greater good they should install something that makes a lot of noise but doesn't damage the car say 5m before before the hard hit. Maybe fine $100 per soft hit to pay for it? They can say well we've just saved you a lot more!

They have flashing lights that go off if your vehicle is too tall.

Re: 11 Foot 8 – The Can-opener Bridge

#114

Post by cam_l »

Animats wrote: post #53

The Sidney Harbor Tunnel had a similar problem. They came up with an elaborate but successful solution.[1] There are detectors and huge flashing warning signs that light up. Then, there's the last-chance sign. At the entrance to the tunnel, pumps force a curtain of water straight down across the entire roadway. Then a powerful laser system projects a giant octagonal red STOP sign onto the water curtain, filling the e…

I never understood the high-tech approach to this problem. Where i am from they have large metal tubes dangling down a ways in front of the bridge. Makes it sound like you have already hit it.

Another more insistent approach I have seen elsewhere is to mount a large steel bar across the road, which takes the top of the truck off before they hit the bridge.

(edit:not very simple problem, obviously..)

Re: 11 Foot 8 – The Can-opener Bridge

#115

Post by loeg »

notatoad wrote: post #110
loeg wrote: post #105

Earlier quoted context omitted.

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.

Re: 11 Foot 8 – The Can-opener Bridge

#116

Post by dbcurtis »

jacquesm wrote: post #43

You have to wonder how much it would cost to dig that out two feet and solve the problem. Likely a lot less than the annual capital destruction.

For how far out? A village near where I grew up had a low railroad overpass. The road underneath had been lowered to create clearance, but not very far on either side. The “low clearance” sign had the height at the overpass marked on it. While technically correct, it only “worked” for modest length straight trucks. The typical articulated truck spanned the depression.

Geometry bites.

Re: 11 Foot 8 – The Can-opener Bridge

#117

Post by Animats »

Invictus0 wrote: post #69
Animats wrote: post #53

The Sidney Harbor Tunnel had a similar problem. They came up with an elaborate but successful solution.[1] There are detectors and huge flashing warning signs that light up. Then, there's the last-chance sign. At the entrance to the tunnel, pumps force a curtain of water straight down across the entire roadway. Then a powerful laser system projects a giant octagonal red STOP sign onto the water curtain, filling the e…

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.

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...

Re: 11 Foot 8 – The Can-opener Bridge

#118

Post by georgebarnett »

cam_l wrote: post #114
Animats wrote: post #53

The Sidney Harbor Tunnel had a similar problem. They came up with an elaborate but successful solution.[1] There are detectors and huge flashing warning signs that light up. Then, there's the last-chance sign. At the entrance to the tunnel, pumps force a curtain of water straight down across the entire roadway. Then a powerful laser system projects a giant octagonal red STOP sign onto the water curtain, filling the e…

I never understood the high-tech approach to this problem. Where i am from they have large metal tubes dangling down a ways in front of the bridge. Makes it sound like you have already hit it. Another more insistent approach I have seen elsewhere is to mount a large steel bar across the road, which takes the top of the truck off before they hit the bridge. (edit:not very simple problem, obviously..)

There are metal bars.

Why do you think the team at the tunnel would go to such lengths and expense if there was a simple solution?

Re: 11 Foot 8 – The Can-opener Bridge

#119

Post by [deleted] »

Animats wrote: post #53

The Sidney Harbor Tunnel had a similar problem. They came up with an elaborate but successful solution.[1] There are detectors and huge flashing warning signs that light up. Then, there's the last-chance sign. At the entrance to the tunnel, pumps force a curtain of water straight down across the entire roadway. Then a powerful laser system projects a giant octagonal red STOP sign onto the water curtain, filling the e…

[deleted]

Re: 11 Foot 8 – The Can-opener Bridge

#120

Post by closeparen »

loeg wrote: post #115
notatoad wrote: post #110

Earlier quoted context omitted.

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.
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