It’s a big I-Beam. It’s designed to ensure the that the driver’s truck takes the full brunt of the collision between truck and obstacle, leaving the bridge itself unscathed. Kind of a dick move, if you ask me, but the state’s sign with flashing lights and height measuring device should provide ample warning against the railroad’s indifference.
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I remember a number of instances in the past when roads were closed for repairs and the people planning diversions didn’t consider the fact that amongst the diverted vehicles would be double-decker buses, or drivers forgot what kind of bus they were driving.
I consider it a good idea. Certainly superior to damaging both the vehicle AND the bridge. Limits the total damage neatly, and concentrates it to the object that can be moved away to repairs instead of having to close one or both roads. And it gets presumably activated only in the cases that would lead to actual damage. (If it is ten inches below the bridge’s edge, then it would be a dick move, though.)
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Consequences and memory that’s a bit more transparent and a bit less corrupt than “self”-regulation? Though spending on a new bridge is another public option.
So the sign is a fuse.
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If I’d want to go a-lawyerin’, I’d say the sign is a protective device, like fuses are. Different actual mechanism but same class of damage-limiting devices.
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or YouTube advertising?
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With a rail bridge like this it’s more usual to just sink the road a bit. Depending on services and drainage it’s almost certainly the cheapest option.
Sump pumps don’t always make the world go around.
Damn. Now I can hear is Danny Kaye singing that.
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I’ve followed this channel on YouTube for a few years now. Good for a low-risk-of-seeing-death dose of carnage every month or so.
The guy has a site, http://11foot8.com, with a handy FAQ. The relevant part to most of the questions here is here:
Can’t the road be lowered?
That would be prohibitively expensive because a sewer main runs just a few feet below the road bed. That sewer main also dates back about a hundred years and, again, at the time there were no real standards for minimum clearance for railroad underpasses.
Can’t the bridge be raised?
Here, too, the question is who would want to pay the millions of dollars to raise the tracks a couple of feet? To accomplish this, the grade of the tracks would have to changed on both sides of the trestle, probably for several miles. That would require rebuilding all trestles in Durham. And NS would have to shut down this busy track for months. I don’t think they are interested in that idea.
There are other tidbits over there as well, such as exactly what sort of measures are taken further down the road before the bridge.
If you’re interested in the European equivalent there’s also this, (pardon the French 
): http://www.2m40.com/
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From the site’s FAQ :
Can’t the road be lowered?
That would be prohibitively expensive because a sewer main runs just a few feet below the road bed. That sewer main also dates back about a hundred years and, again, at the time there were no real standards for minimum clearance for railroad underpasses.
I see. So a conventional job is out. But “just a few feet” can (or can not) be enough, if some uncommon approach is used.
Now, how deep is the sewer mains? How many inches are needed to lower the bridge incident rate by say 90%, what’s a nominal bridge clearance? The area over the mains is rather short, and some more advanced approach than conventionally layered road could be used over that 2-3 dozen feet, something with much thinner structure (perhaps a flat steel “bridge”?), without affecting the sewer mains.
But all now depends on counting inches, and how (and if) can we get at least as many as we need.
I’d suggest putting together a histogram of vehicle heights that do make IT through. If it is bimodal, it just might be worth shrinking the opening height to make it visually obvious that tall vehicles can’t pass. That could be done by raising the road bed or dropping that beam by a good 3’.
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In Italy, we use this kind of visual and “acoustic” warning:
if your truck hits the hanging metal stripes, then you’ll hit the bridge ahead (there’s a railway bridge 200-300 meters after the “warning” sign)…
I remember reading a story about a highly successful and wealthy financier. He confessed to his therapist that all he really ever wanted to do was drive a delivery truck. As his therapy he got a weekend job as a delivery truck driver.
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I don’t know that I would agree that it’s a “major” problem. On average, one truck a month hits this bridge. The box part of the truck is damaged or destroyed, but the vehicle typically isn’t. No one is injured. It causes a temporary inconvenience to traffic for an hour or so once a month, and lightens the wallet of the idiot driver. That’s not a serious enough issue to warrant spending millions of dollars to permanently fix it.
A agree that “a few feet” sounds like a lot to play with under the road, if you’re just looking for a few inches.
The bridge could also be modified for clearance without changing the grade of the tracks. Much of the structural work of the beams could be transferred to trusses that are above the line of the rails and alongside the tracks, and the beams theselves made much shallower. Higher strength materials would also help.
I guess it all come down to cost. But I’d bet that there are solutions that do not require re-grading kilometres of track and rebuilding tressles.
One thing I haven’t seen addressed, is if the municipality gets fines off these truck drivers. If they have a hit a month, at say $2k/fine, it might be more profitable to do nothing.
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Also, there are usually several warning signs before the bridge, some with flashing lights. This is the main reason Ryder Truck Leasing stopped renting to Joe Customer. Who ever hits the bridge, pays for the repair of the unit.
