Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'... 4

[VEBill]

"So my assumption....is perfectly correct."

That's perfectly incorrect.

Edit: Extraordinary claims require extraordinary evidence.

 

[Alistair_Heaton]

They would be better restricting the width of the two lanes so only cars can get through.

I used to drive 40 ton artics in my youth and around Scotland there are a fair number of similar restricted bridges which regularly get hit with lorry's that are not in the know. Quite a few of them listed as cultural items which need protection.

Drivers will see and not go near narrow openings. They can see the limitations of the front of the vehicle, they can't see the roof. 4 elephant posts both sides of the bridge with a car width between them will do the trick. Two next to pavements stopping them going on it and the other two in the middle restricting the width. Also has the bonus of giving a pedestrian safe heaven in the middle while crossing.

 

[3DDave]

VEIBLL - then you should be able to write a concise statement to the contrary rather than gainsaying the negative.

 

[3DDave]

So they won't hit the bridge but now have road level impacts with obstructions that prevent emergency vehicle access? In the USA roads typically don't have posts directly in the middle. Distracted car operators now have something to hit that they did not expect. Smashing.

Looks like a no-fail plan; here it is in action:

https://www.dailymail.co.uk/news/article-4600048/John-Lewis-lorry-rescued-got-stuck-narrow-lane.html

https://www.alamy.com/stock-photo-w...k-in-narrow-street-in-barcelona-42024959.html

https://www.dailymail.co.uk/news/ar...GV-narrow-alley-blindly-following-satnav.html

https://www.driving.co.uk/news/news...-navs-keep-sending-them-down-too-narrow-road/

- "Drivers ignore 6ft width restriction sign", "in the past week alone, three trucks have become stuck in it."
- three a week is not an improvement over the current situation.

 

[VEBill]

The internal logic (sic) that was used to reach (for example) this conclusion, "So raising the bridge to any height is a flawed approach", clearly indicates that rates of occurence (i.e. numbers) are not being considered.

That's a blindspot that is a subtle form of innumeracy. A sort of 'Black vs. White' digital processing that is effectively a Random Opinion Generator. This type of cognitive bias allows arguments to be made that are grammatically correct, but reach the most extraordinarily bizarre conclusions.

 

[3DDave]

The goal is avoidance of impacts. Changing from X per year to Y per year, where X ~ Y, at some large cost is a blatant form of innumeracy.

Perhaps you could do the work and see what the change in rate was from the addition of the red light and blinking sign. That would likely show that the desired reduction, but not elimination, has already been achieved but, since no one has stated their lower limit acceptance for collisions, the clear assumption has to be that that number is zero. Which won't happen.

I think you don't know what "(sic)" means.

 

[epoxybot]

Why not install a Railroad Crossing Arm that doesn't budge until the vehicle that is the height hazard is out of range?

 

[3DDave]

Because the detector has to be far enough back that a truck at full speed has time to stop; if cars are already stopped to allow cross traffic and a truck trips that detector, the truck will never be able to move because the cars ahead of it will have a solid red light/crossing arm blocking their way.

Now, as the Australian experiment goes, 24/7 manning of the bridge could put a person there to handle this deadlock, but I think the budget for 3 shifts a day of two people to cover for lunch and bathroom breaks is more than they want to spend.

 

[davidbeach]

Raise the bridge but don’t change any of the signage or the warning system. The number cases where the truck is only 3-5 inches too tall will be greatly reduced.

 

[Alistair_Heaton]

Works fine in uk, ambulances have a remote that drops the posts in middle if required.

Fire brigade have zero chance getting under it anyway. Police cars fit through.

Two bracket bollards are different to narrowing streets and medieval corners.

Mind you UK drivers can do roundabouts which I suspect would be leathal in the USA.

 

[VEBill]

"...the clear assumption has to be that that number is zero."

Nonsensical assumption leads to nonsensical opinions.

It's one thing to pretend to be daft on a social forum for entertainment purposes, but I really hope that you don't do serious engineering work like that.

 

[3DDave]

VEIBLL - Then what number do you pick? How much is it worth? How often do you resort to insult instead of analysis to force your opinion on co-workers? That's not an argument, that's bullying.

Alistair - If a driver cannot notice two entire buildings are too close together then they won't notice small items planted in an unexpected location. A remote? Come up with a link showing these in the middle of London streets for truck control. There are traffic circles all over Washington DC; US drivers handle them fine. But the number of low bridge collision stories in merry Old England is stunning, so you haven't much evidence of any superior skills there.

Edit: Used correctly bollards are a great idea for this

https://www.youtube.com/watch?v=IELpd43PMvk

Instead of damaging over height vehicles they can potentially damage everyone else.

Edit 2: Cambridge put rising bollards in. Then Cambridge took them out because of continuing damage. Huh. Who would have guessed?

https://www.cambridge-news.co.uk/news/cambridge-news/cambridge-rat-run-anpr-roads-13014779

Now they use Big Brother ticketing cameras.
"An ambulance, on the way to a treat a fallen child in the city centre, was forced to make a detour because the bollards in the road failed to go down." Perfect example.

 

[Alistair_Heaton]

They manage and they are not small.

And painted black and yellow.

https://www.access2time.co.uk/security-gates-barriers/bollards/

They are also used to control access to pedestrian areas.

And London has loads of them mainly used to protect against lorry attacks against pedestrians. They are tested for a 40 ton artic hitting them at 50 mph.

Problem with English roads is most of them are chariot sized or horse and cart same with road curvature in market towns. There are loads of bridge hits as well, there is also the problem with double decker buses which when they do hit tend to kill the whole of the top deck.

Most commercial drivers in the SE of England are not locals. Its a 200 year old road structure with no space to expand the road width.

I can't see them getting rid of hydraulic bollards any time soon.

 

[JohnRBaker]

Yes, I've often driven around the Midlands, places like Nottingham and Leicester, or out west of London to places like Salisbury and Andover. and what always struck me was that for a country famous for some very large cars, like Rolls' and Bentley's, they had some of the narrowest 'country lanes' I've ever seen, often with hedgerows that would have made it impossible for two cars like that to pass each other. I always rented something small like a Mini or one of the smaller Fords, simply because of the narrow roads and having to find places to park, particularly in older cities like Cambridge or Grantham.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Alistair_Heaton]

You just need to look at the maps of these place in the 1600's and then 1700's then 1800's, London benefited of a reset with the fire of London. Most places didn't.

Country lanes for hundreds of years were only for the transport of product to the farms there was no need of more space, traffic only went in one direction depending on the time of day. These days some of them are main routes between population centres.

Up north in Scotland we didn't benefit from the Roman roads but due to much lower population density the roads are much less restrictive. What we do have though is a load of railway bridges of none standard height which do cause problems. More than half of them aren't even active but are of historical importance. All of them are made out of arched brick so there is no chance of adjusting the height to add an extra 8" on.


large cars/lorry's have only existed for the last 100 odd years, the road network start evolving with the Romans in England.

 

[VEBill]

"Then what number do you pick?"

That's where engineering analysis comes in, in a small report and/or spreadsheet. As opposed to taking extreme positions, as you have.

 

[3DDave]

VEIBLL,

Ah, blame shift to a "report". Very few such reports get done. Engineering is generally to maximize or minimize, based on some resource limitation. So one either picks an amount of money to spend and gets the most for it or picks an outcome and tries to spend the minimum to achieve it. The latter was the case for every proposal and contract I worked on for the DoD.

They are spending $600k and closing the underpass for 2 weeks solid. I expect both of those numbers exceeds the last 20 years expense to the city for responding to crashes and the total time the underpass was closed while jammed vehicles were removed.

Based on your economic experience, would you agree that this paying off, without including the time-value of money, in more than 20 years is a wise investment?

The sad thing is this won't prevent -all- crashes. As I previously pointed out, there are many bridges that share the new height or are higher which are hit regularly. They aren't as noted because they don't have a website dedicated to them. So it is likely to stretch this investment payback to 30+ years.

To demonstrate that is expected, they are installing a new crash beam.

 

[3DDave]

Just found this:

 

[1gibson]

Horizontal and vertical are easy, the diagonals look like it will take another few pages to get.

 

[3DDave]

Looking at the Sydney Harbor tunnel -
1) The water curtain stop sign is manually operated. I assume this is because traffic speed is variable and they don't want a car getting rear-ended while stopping by the truck it is actually for, so they carefully observe the monitors to operate it at exactly the right time.
2) They say they decreased the incidents by one third simply by instituting a 2000 Australian dollar fine; they also pull the license for 3 months.
3) This is not for ordinary trucks; this is for legally over height vehicles, so it's a tiny fraction of traffic.
4) The sensors on warnings like at the Durham bridge that are ahead of this are set below the marked tunnel height, so drivers of vehicles don't know what the limit actually is; gets fined 2k anyhow.
5) Because it's last-ditch, an onsite crew has to be available 24/7 to block traffic while the over height vehicle backs up to a place, 500 meters earlier apparently, to where it can divert.
6) My favorite, one trucker was going to get a fine because a thin sheet-metal panel, about 500mm square and <1 mm thick was peeled up and waving in the breeze on his ordinary height semi trailer. And lose 3 months of work.
7) Even with this system there are still truckers who manage to hit the tunnel; they just have to be far more creative, such as letting the load slide partly off the side but still be too tall to get lifted by a fork truck back into place.