On a recent road trip we saw an Oversize Load truck on the freeway. In addition to the very common vehicles that followed the truck with the load, there was a less-common lead car. Well, actually, it may have been a small pickup truck. Regardless, it had a tall pole affixed to the front of it.
We surmised that the point of the pole was to assure that the overpasses were high enough to allow the truck with the oversize load to go through without problems. Is this the reason for the pole? If not, what was the pole for?
If the purpose was to assure the truck had sufficient clearance, what would have happened if there wasn’t enough space? I get that the truck with the load would have stopped before attempting to go under the overpass, but what then? This freeway had two lanes in each direction, with a median “gully” in between. Even if protocol is to somehow stop traffic (I would guess by having the state police help), there didn’t seem to be enough space to turn the truck around. I don’t think the truck could transverse the median to get to an exit so that the truck could avoid the overpass. Would they have stopped traffic from far enough back that the truck could go in reverse to the exit? This could be several miles.
Yes, it’s to make there’s enough overhead clearance for the oversized truck. IIRC, the very top of that ‘pole’ usually bends. I assume if it bends back it sets off an alarm in the cab.
As for what they would do. I assume the first thing they’d do is get out and physically measure the height from the ground to the obstruction. It’s possible the truck may fit, even if it means they have to move to a different (lower) part of the road. Be it a different lane, the median or even the oncoming side.
If it’s really close, say within an inch or so, one option (and I don’t know if they do this in this scenario) is to let some air out of the tires. That may buy them the extra space. If they go this route, I’m sure it would be after lowering the suspension as much as possible.
If this just isn’t going to happen, they’d have to backup to the previous exit. There really aren’t any other feasible options.
Having said all that, I would have thought common practice would have the lead car well ahead of the convoy, say at least a mile or two. That way if they have an issue there’s an exit between the truck and the obstruction.
If it’s a diamond intersection on an interstate highway, they ‘might’ be able to go up the offramp, and then down the onramp. And I imagine the pole is a few inches taller than the heavy load. If it has a few inches, they may be able to creep under it with eyeballs on it. But yeah, the should know first, but mistakes happen. Hell, we sent a spaceship to mars using the wrong mathematical units.
Unless someone physically measured them, the signs aren’t always correct. I know of one bridge that gets hit a few times a year even though the trucks are lower than the stated height. At one point, the signs were correct, but over the years the road has been paved and repaved and those few extra inches of asphalt make for less clearance. IIRC, there’s also been some work on the bottom side of the bridge that makes it even lower.
Another issue would be if the road dips at all as it goes under the bridge. The height from the bottom of the bridge to the road could be correctly stated, but a long truck will have problems.
A few years back I briefly spoke with a guy in charge of moving a disassembled vintage airliner across the country. I’m gonna go from memory while I try to find his site but the gist of it is this: the incredibly detailed move plans are wrong. Frequently. In his story, he said that the move plans were developed and approved by state transportation agencies that seemingly worked with out of date route information.
They got stymied several times and had to get reroutings approved on the fly. More if I find it.
You want to see bridges being hit? Take a look at the video compilation from the 11 foot 8 inch bridge. It has been filmed being hit hundreds of times. It’s quite famous.
Several years ago a big rig was tooling down I-5 (you know, the main route between Vancouver, BC and Mexico) just north of Mount Vernon here in Washington State, with a pilot car 2 or 3 hundred feet ahead. And this pilot car had a pole mounted that was supposed to smack on anything too low and give warning. However, there were several problems with this scheme; mainly that the truck was following too close to the pilot car to allow time for any reaction to occur before it was much too late.
Anyway, the truck, which was way too close to the edge of the roadway anyway, clipped a main cross member of the bridge, and down came the span. A photo of the downed bridge is shown in the following link (if it works).
I will say the I’ve never seen the State of Washington react faster to a crisis. They had a replacement span in place just over a month after the accident (using a WWII Bailey Bridge), and a permanent replacement for the span within four months. It’s amazing how fast an Environmental Impact Statement can be written and accepted when push comes to shove.
The trailers that carry abnormal loads are often height-adjustable. They would want good ground clearance for normal driving so that they would not ground on humps. The road under a bridge is either level or a dip, so the trailer frame can be lowered to within a few millimetres of the road surface.
Over here we get many (far too many) bridge strikes, but none that I know of that were from abnormal loads, which have all kinds of regulatory hoops to jump through before setting off.
Wires and trees also are a hazard. Wires can be lifted up to pass under. changes in polls and wire work and other factors can have wires sag lower then expected. Trees may have grown in to that area that was once listed with a certain clearance.
It’s a final check and much easier to decide what to do about it safely stopped roadside with time on your side, even with a ticket in hand if that were to happen, instead of wedged under the obstacle. At which point one can come up with a remedy.
So I know you were all dying for this. I found the site, link below, but all the images are dead. Here’s the piece that backs up what I heard in person.
Yeah, it’s just sheet metal. You can see how weak it is when a semi rolls over (and lands on it’s side) and all the contents dump through the top like they built it out of construction paper.
The detour was a PITA when it collapsed. I drive over the Skagit River bridge four times a week. Mrs. L.A., not so much. Every time we cross it she says, ‘There’s the infamous bridge,’ often succeeded by ‘I hope it doesn’t collapse while we’re on it.’
It continues to surprise me how trusting people here are that “things just work”. That the route info has correct heights, etc.
No, they don’t work 100% of the time. So you make plans for those times when it doesn’t.
(I was just talking about a bad GPS route this AM. A straight half mile shot on a main road is instead given as a zigzag taking side routes. No. Do not trust these things to be right all the time.)
You would think that U-Haul and Penske and Ryder would warn their customers about this. But obviously not.
My favorites are the cautious camper at the 5:01 mark who slows down to a crawl but still manages to wipe everything off the top of his travel trailer. And then at the 6:15 mark are the two trucks loaded with bales of straw. After the first one loses the bales of the top of his load, his buddy follows and does the exact same thing.
