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How would you use electronics to solve the 11' 8" bridge problem
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drussell:

--- Quote from: mariush on January 07, 2018, 09:25:42 pm ---Laser or infrared sensors on each of the three sides  (trip the sensor if the truck is within 1-2 cm of the maximum height of the tunnel )
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From 11foot8.com:


--- Quote ---The city of Durham has installed “low clearance” signs on each of the 3 blocks leading up to the trestle (Gregson is a one-way road). There is a sensor that triggers an LED blackout warning sign when In overheight vehicle approaches the trestle (more info below). Several blocks ahead of the trestle the speed limit is 25 MPH. The folks from the city planning department said that they made an effort to prevent accidents.

The signage is good, and the vast majority of truck drivers notice the problem and avoid the bridge. Large signs alert driver to the low clearance several blocks before the bridge. Half a block before the trestle, a sensor detects overheight vehicles and triggers an LED blackout warning sign that was installed in May 2016. That same sensor also triggers a red-light phase at the traffic light directly in front of the trestle (installed in March 2016), so the driver has 50 seconds to read the warning sign next to the red traffic light and consider their next move.
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Hmm..  In some ways I suppose it's like chess for truck drivers.  Consider their next move...  :-DD

BTW, the clearance to the crash bar is actually 11 feet, 10.8 inches....  At the outside edge of what they're allowed to have the sign show below the actual clearance.  (The sign must be withing 3 inches of actual clearance.)  This already gives drivers the maximum allowable leeway in what they think their height vs. the actual clearance is.
drussell:

--- Quote from: Cyberdragon on January 07, 2018, 09:42:56 pm ---
--- Quote from: NiHaoMike on January 07, 2018, 09:15:32 pm ---Low tech solution: a steel beam hung (by chains from poles so it's still free to move) an inch or two lower than the bridge a few tens of feet before the bridge. Colliding with it will make a loud noise, but with far less damage than colliding with the bridge itself.

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Allot of parking garages have these. They have a pipe hanging in front of the entrance with the height limit marked on it.
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Bars or chains won't work, you have to be able to turn onto the truck route road:


--- Quote ---A low clearance bar is a bar suspended by chains ahead of the bridge. Overheight vehicles hit that bar first and the noise alerts the driver to to the problem. I understand that this approach has been successful in other places, but it’s not practical here. There are many overheight trucks that have to be able to drive right up to the bridge and turn onto Peabody St. in order to deliver supplies to several restaurants. Making Peabody St inaccessible from Gregson St would make the restaurant owners and the delivery drivers very unhappy.
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tszaboo:
First of all, this clearly would have been avoided with the metric system. No doubt about that.

They usually place overhanging chains before bridges like this, 10-15m which hang lower than the bridge.

And if 126 documented crash happened here... Clearly it is bad design, not driver problem. Make it lower. Make it so, that it is clear that you cannot pass. Like every car can pass, and jerks with their empty Ford F430 get their roofs shredded.
drussell:

--- Quote from: Gyro on January 07, 2018, 09:41:40 pm ---- The signage is confusing. The driver  is probably still trying to understand the grammar of "OVERHEIGHT MUST TURN" when he hits the bridge.

- The actual height limit sign is small in comparison to the above one, the driver probably doesn't even notice it while trying to decode the other one. If you asked him, he probably wouldn't have even registered the figures.
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That is only the last set of warnings.  There are signs for blocks before that to warn of the impending trouble.  One set even has the detector on it and flashes warning lights on the signs (even well before that last intersection intersection) that basically say "YOU ARE OVERHEIGHT!  YOU MUST TURN!"

People still smash into the bridge going through the red light.  :palm:
drussell:

--- Quote from: RoGeorge on January 07, 2018, 09:47:50 pm ---Obviously, some drivers are direct descendants of Big Foot. Switch to metric!  :-DD
--- End quote ---

--- Quote from: NANDBlog on January 07, 2018, 09:53:11 pm ---First of all, this clearly would have been avoided with the metric system. No doubt about that.
--- End quote ---

Yes, of course metric would solve the problem.  Everyone knows metric solves everything.    :P


--- Quote ---For the convenience of our metric-only audience, here are the measurements we’re talking about in Meters:


* 11foot8 (11 feet 8 inches) = 3.556 meters
* 11 feet 10.8 inches = 3.627 meters
* Safety margin: 7.1 cm (at the crest of the road)   
Would this situation be better if the signage were metric? Well … take a look at his website: http://www.2m40.com/ (Warning: French. Metric)
--- End quote ---
   

(many LOLs...)


--- Quote ---And if 126 documented crash happened here... Clearly it is bad design, not driver problem. Make it lower. Make it so, that it is clear that you cannot pass. Like every car can pass, and jerks with their empty Ford F430 get their roofs shredded.
--- End quote ---

It was built over 100 years ago and it's not likely to be rebuilt anytime soon.  :)

It seems like it works just fine, with only the most inattentive having their "roofs shredded."  Hilariously.  On camera for all to see.  Exquisite!  :)
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