Ever stopped at a red light and noticed something odd about the poles holding up the traffic lights? Look closer next time—many of them appear to hover just above the concrete, anchored by visible bolts. This video below explains it all. It’s not a job left unfinished. It is actually clever design, and all about functionality and easy maintenance. Let’s break down why engineers prefer this so-called ‘floating’ base plate setup.
At first, you might think mounting poles directly into concrete would be more stable—after all, that’s how heavy columns are often installed. But traffic light poles are lightweight, hollow, and face constant wind pressure. Instead of brute stability, they need flexibility and precise alignment. Enter the standoff base plate. By resting on leveling nuts, these poles can be fine-tuned for perfect verticality, even when the ground shifts slightly over time. That’s critical for keeping your 30-foot pole from leaning like the Tower of Pisa.
The open design also simplifies maintenance. If the pole tilts after years of wear, it takes just a few nut adjustments to fix it—no heavy cranes required. Plus, the gap helps prevent moisture buildup, reducing corrosion. So next time you’re waiting at an intersection, you’ll know it’s not just clever engineering—it’s practical street smarts. If you’re an infrastructure nut, this slightly older article might spark your interest.
Also if a car hits them its better if they just snap at the base
I thought that was the reason for this. Interesting to learn it’s more than that.
Video says they aren’t supposed to break away at all. huh
There are two different types (I believe). They don’t want traffic light poles to drop on traffic, whereas stop signs are fine to fall over and there the priority is not screwing up the foundation so it’s easy to put in another one. Those have a base plate that looks fairly different from this type.
Sorry, accidentally pressed on “Report Comment”, on this comment on my phone and was just scrolling. Mods plz disregard.
My original comment about them shearing at the bolts was entirely an assumption that 4 bolts embedded in concrete would be the weakest point, not based in any research at all. so I’m glad to see others info and opinions in that matter.
Everyone says clever, but the answer is lever. You simply give the resulting lever arm of a force no solid object that would resist and increase the force. A crowbar only works too if it rests against a solid barrier to pry open a door.
They do the same with free-standing towers and pylons for wind turbines.
Oh, so it has nothing to do with being less of a hazard in motor vehicle accidents? I imagined these “floating” pole mounts were designed to shear off when struck. Hmm… Maybe that’s a different, clever design.
Only small poles are designed to shear. At some point the structure becomes large enough that it is more dangerous for it to topple over the road than for one car to crash into it.
There are poles that are made of very thin aluminium rods welded together a bit like lighting trusses, I believe those are designed to buckle and snap very easily in high risk areas. I can’t find an image on google but it did lead me down a rabbit hole that led to the IHE’s guide to roadside structures:
https://www.theihe.org/wp-content/uploads/2023/12/IHE-Sign-Structures-Guide-2021.pdf
Looks like there’s also breakaway joining nuts for the type in the article so they could be (retro)fitted with those if needed.
A family member had a solar plant installed at their house recently, I went to watch the installation.
They drilled into the slab, put in some kind of epoxy in the holes (I have no idea what it was, all text was in chinese), put stud fasteners in and then bolted the solar prefab structure base a few inches above ground, and finally encased the legs in cement.
I still have no idea if they did a good job or not. It seem really solid so I sure think so
I’ve got a pack of resin anchor bolts for the brackets to mount an antenna pole to the side of my (brick built) house, if the pack (and the engineer I chatted to when I bought them) is to be believed and I clean out the holes properly then the bolts are likely to outlast the house.
Not sure how I’m supposed to remove them if I decide I want to, I suspect it may involve a very large hammer and chisel.
naaaah, just hit them with a hammer axially. Glue should break and bolts shoudl be free. -ish.
Nope. :-) At least, it is not likely. Modern “chemical bolts” use resin that is specially formulated to bond on a molecular level to the metal of the bolt AND penetrate in the mortar/bricks/… around them. So even dynamic forces (like a hammer blow) are distributed in a large area of the wall. I think, a good metal saw might be the solution…
To remove chemical anchors you’re not supposed to use brute force but heat – like from propane blowtorch. Once the resin burns out, it’s easy to remove.
You don’t remove them, they’re permanent. I mean I suppose a jack hammer could be employed, but if you really need the threaded part gone, cut it flush with the brick and paint it to hide it. Or use wedge/sleeve anchors, they are more removeable (though still not easily if they were installed correctly).
Just remove the entire house around them so that only the bolts remain, duh!
I worked in a mine where they used DYWIDAG threaded bars and a 2-part anchoring epoxy resin to support the back (ceiling) from collapsing. They’d just spin the threaded rod to mix the epoxy, but there are lots of anchoring epoxies. Not an issue in a mine, but as far as I know the biggest threat to even structural epoxies is pretty much UV resistance.
Post-installed anchors are usually either chemical set (which is a two part epoxy in most cases) or mechanical friction anchors (often called wedge or sleeve anchors). They’re called post-installed because they go in after the foundation slab is poured and cured, not cast into the concrete. After which, either the entire thing is encased in concrete (not cement) or the space between the base plate and the concrete foundation is filled with grout. Source: I am a PM for an heavy construction company.
What does encasing in cement do? Cement gets blown away by the wind, if not mixed at least with water.
*encasing it in cement
Edit option would be nice. A couple of minutes of edit time, for example.
Three bolts would be better, the four-bolts configuration may be a human interface thing.
I guess this approach works, as it seems to be in widespread use. But the use of fasteners in this way somewhat creeps me out. The bolts themselves are subjected to the full varying loads.
In typical bolted joints, the bolt is meant to carry a near-constant preload, clamping two parts together at their interface. Any varying loads are then mainly transmitted through this clamped interface, and NOT through the bolts themselves.
Dynamically loaded bolts are typically considered bad practice, as they are prone to fatigue failure because of the stress concentration at the thread root.
But hey, I must be missing something, as this clearly works in practice and is described in the video as an engineering marvel… But I surely would not design any highly loaded connection in this way.
I’m not buying most of the explanations in regards to why they are floating.. no one is ever going to re level a installed pole
It should be leveled then grouted so the bolts don’t have to take loads they were never meant for. So I agree it creeps me out seeing threaded fasteners used this way and it’s excuses are just a hand wave of why they did a half assed job
We build gas stations and during the canopy phase the red iron columns are put up much the same way as shown here however they are then grouted in the way you are explaining I have always felt that this method is the best bet
But then the ground shifts and your nice level pole is off kilter. This isn’t just done with little traffic poles. I’ve also seen it with those 150-foot transmission poles too. The interesting part is that, if you a clever with your wrench, you can level the pole without a crane or any heavy equipment. You just back one bolt a little, then tighten the opposing bolt.
“The interesting part is that, if you a clever with your wrench, you can level the pole without a crane or any heavy equipment. You just back one bolt a little, then tighten the opposing bolt.”
Ding ding ding. This is the answer: Lower installation costs/faster completion. The rest is just hand waving.
FWIW in the town I grew up in, there were some of the MASSIVE overhanging freeway signs that had a ring of threaded rods around the base (16 of them IIRC). One of the signs broke loose and guillotined a carload of people. Only three of the nut pairs had ever been installed. On inspection, they found a bunch more missing plenty of fasteners.
No one is leveling a 150 transmission pole with a hand wrench. Ground subsidence is not something you solve by adjusting the anchoring nuts.
I worked in a mine where they used DYWIDAG threaded bars and a 2-part anchoring epoxy resin to support the back (ceiling) from collapsing. They’d just spin the threaded rod to mix the epoxy, but there are lots of anchoring epoxies. Not an issue in a mine, but as far as I know the biggest threat to even structural epoxies is pretty much UV resistance.
Brady from Practical Engineering did a similar video about 3 weeks before this video: https://www.youtube.com/watch?v=nGa1244hK9Y .
This video is a bit of a ripoff of that (but about 1/5th the duration while covering the same gound (pun intended), which is a win)
Grady ;)
I know from experience what happens if you dont do this. Condensation inside the metal pole will collect at the bottom and hang out until your pole corrodes from the inside out.