There is no mention of installing a sturdy beam across the road slightly lower than the least clearance, just a suggestion that the least clearance should be reported, and an extended discussion of the multiple (and rather unsurprising, IMHO) ways in which the pilot car system failed.
I am reminded of the half-assed measures that were taken to mitigate the risk of DC10 cargo doors blowing open, prior to the Turkish Airlines crash in Paris. Am I missing something here?
Sadly, there's not much that can be done to fix humans.
The elevenfooteight bridge now has a traffic light which goes red and stays red on detecting an overheight vehicle, with a lit-up sign saying "OVERHEIGHT MUST TURN". It's still getting hit by overheight vehicles.
And then there's the lengths that had to be gone to in Syndey to stop overheight vehicles entering tunnels:
The 11'8 bridge does indeed seem a lost cause as far as preventing people from ruining their overheight vehicles. But the problem for the bridge has been solved: they installed a beam in front of the bridge which takes the impact.
The same sort of thing could be done with this bridge. Install a sturdy beam ahead of the structural bits. You won't stop people from driving overheight vehicles onto the bridge, but you will stop them from destroying the bridge in the process.
You could have sacrificial beams in front of all the important ones throughout the bridge, if you're worried about lane changes. That may not be worthwhile though.
Right, so you'd need a lot of sacrificial beams if you wanted to defend against lane changes in the middle of the bridge. Probably easier to add structural redundancy instead.
The water is right at the tunnel entrance, not in the area where you would be braking to avoid impact. By the time you've reached the water you will have collided with the top of the tunnel, which should go a long way towards helping you slow down. Literally 'idiot proof' design right there.
Sturdy beam is a great idea. Better to rip off the top of the Truck, and maybe give one driver whiplash, than to take down an entire bridge. Surprised it isn't the default case where bridges are at risk.
I can't find the article now, but there was a state somewhere in the southern US which had great success in reducing bridge strikes by setting a row of cowbells. It seems that the sound of many cowbells suddenly hitting the front of a moving truck can really get your attention.
It depends what the risk is. Chains followed by a beam are probably better, but the driver was already not paying attention when they passed warning signs.
If the bridge collapses, other vehicles can be damaged, or people killed. Especially if it's carrying a road or railway.
Maybe do both. But the idea of the Sturdy Beam is that it's about 500 milliseconds away from a structure which will collapse if hit - after all of the warnings by the drivers have been ignored.
There's a low underpass beneath a railway track near my house that claims at least one panel truck a month (usually beer trucks). It's an old rail line, and the underpass arch is faced with granite. The trucks don't win.
I-25 in Denver near 20th St. and 23rd Ave. has clear indications painted on the bridges and the signage before the bridges indicating lower clearance on the shoulders. It's not that hard to do.
NYC takes the cake for inaccurate bridge height signs, though. Some bridges have signs indicating 12'9" or lower clearance when standard 13'6" trucks can clear them easily. It's a complete mystery why they can't mark them correctly. It's been this way for decades (literally).
I got burned by this in upstate New York and it caused an unnecessarily long delay. I was following the directions provided by the customer and came across a 12'6" marked bridge towing a 13'6" trailer on a narrow two-lane highway. I stopped, obviously, and had to ring the highway patrol for help. Traffic behind me was stuck waiting and this low clearance bridge was not properly marked in the trucker atlas and (if it had truly been 12'6") not up to spec for a state highway overpass. I'd done my due diligence so this was the highway patrol or customer's problem to sort out.
About an hour and a half later, we established that the road had been recently re-paved and no one was exactly sure what the height was. Backing up to the nearest intersection was not an option because there were none close by and turning the tractor-trailer around was impossible. The cops were cool about it and suggested that I creep forward very slowly and see if I'd fit. I was able to do this and stop just as the trailer reached the bridge. I got out of the cab and climbed up behind the tractor to have a peek and had about an inch to spare. I went for it, very slowly, and made it under. No fun but I did get a cool photo as a memento: http://i.imgur.com/64uYu2z.jpg
I took a different route on the way back of course!
No, this is not practical and you risk damaging the tires. It is possible to deflate the air ride suspension for the tractor drive axles to drop a few inches (useful for backing under a new trailer when the nose is low) but I did not do this because the rear of the trailer would still be too high.
Not one of my finest but it is a view leaning out the driver's window and looking up and back at the top front left corner of the trailer, with the (very dark) bridge girders looking like they are resting on the trailer. There's about an inch of clearance and I am just coming out from under the bridge, nearly to the edge, with most of the trailer yet to pass under. Very difficult to see though, I really needed more flash but I was concentrating on other things and holding up traffic.
The positioning of the sign doesn't help - so high up. Who looks up that high when driving?
The truck driver doesn't realize the sign is only on when he is there, he never sees it when it's off, he has no idea it's illuminated specially for him.
This is government saying "We did something", while doing nothing.
Someone driving an oversize load can reasonably be expected to check their route for clearance. It's not the same situation as some guy trying to find Taco Bell in his RV.
"The driver was following the pilot car too closely: more than half the recommended distance for adequate response (400 feet, or a five-second response time, instead of the recommended 865 feet, allowing for a 10-second response time)."
Er, that's less than half the recommended distance. How did the copy editor let that through?
"that doesn’t account for the economic losses that the area felt because they and visitors no longer had access to the interstate"
I've got a pretty awesome picture of me and my son standing in front of that empty section of bridge from the detour route. They essentially routed I-5 traffic into the town and across another bridge. If I had to guess, the stores in that area probably made more money during the detour...
This is the first I've heard that the I-35W Mississippi River bridge in Minneapolis was "fracture critical", and even if it was, the design flaw of too small gusset plates would possibly make that moot when one of them gave way, since others that were too small would then fail more easily.
No, it isn't, and this is one of the problems when the "general public" comments on engineering things. It's not that people aren't capable of understanding; they lack the experience to understand why something is the way it is.
Someone on /r/seattle[0], where this was recently posted, put it more politely than I:
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It's because that extra two feet can be valuable when carrying oversized loads. Frankly, this all falls on the driver of the oversized vehicle, the driver of the pilot car, and the hauling company.
- The driver of the oversize vehicle is responsible for knowing his load height. A hauler I've worked with before has it in their manuals that the driver must personally measure the load if there is any question. That driver must also stay far enough back of the pilot car to stop in case of a problem.
- The driver of the pilot car fucked up royally by missing the sound of the height-verification antenna hitting the bridge. That is a massive error that should see that pilot car driver drummed out of the industry.
- The hauling company erred drastically by not pre-running the route, or at least the low clearance segments, to verify where the clearance exists. That is "oversize hauling 101."
The article says the state "rubber stamped" an oversize permit. No, they didn't. The hauler certified that the hauler had pre-run the route. It is required that the hauler state that the route has been verified when the permit is issued.
"It is the responsibility of the permit applicant to check, or prerun, the proposed route and provide for safe maneuvers around the obstruction or detours as necessary."
Pilot car should have backup Radar/Lidar as well as the antenna to detect if no sufficient clearance. Likewise, there should be constant electronic Comms back to oversized load, with deadmans trigger + visual cue if the insufficient clearance height is hit. You can add the (almost certainly to be 100x less reliable) human in the chain if you want, but that should be in addition, not instead of.
The Oversized truck should also have an electronic map, which captures cautions regarding height speed issues along every part of the trip.
Simple technology, with a bit of process, could eliminate about 95% of these errors that likely exist today.
Of course, that 5% will still bite from time to time.
What you are saying makes no sense and certifiably wrong because a team of experts recommended changing the standard to ensure min height is always reported, not max height.
Both heights should be available. If only one number is to be reported, then yes, report the lowest height. But, for more advanced scenarios, such as electronic Maps, you should report the lane heights as appropriate.
It's a good design for 99% of the time and a very good design from a high speed traffic flow point of view. It requires minimal ramp up to crossing a feature that is nearly at the level of surrounding land.
The correct engineering solution is to have diversity of designs, including an 'open top' bridge near by, which can serve the other cases as well as critical backup traffic during the failure.
You might note that most of the preventative measures outlined do not modify the design of the bridge, but focus on actually keeping records that track the more critical /minimum/ clearance value, as well as more accurately detecting and reporting to the traveling 'over-sized' vehicle that an abort condition has been reached.
I am reminded of the half-assed measures that were taken to mitigate the risk of DC10 cargo doors blowing open, prior to the Turkish Airlines crash in Paris. Am I missing something here?