Road guy rob! I love your videos. Unlike most educational videos you actual go to the source and film in the field rather than doing it all with voice over and stock videos and photos. I really appreciate all the work you do for your channel. Keep up the great work!
@@RoadGuyRob i love your videos more than Not Just bikes’ videos. You present information in an interesting way that is entertaining and less “wah” moment than some urbanist channels.
It's not just natural wind. Back in the '90s New York's DOT found an overhead sign structure that was bouncing every time a truck went under it. They inspected it and found it was starting to crack. If I recall right, they changef their design standards to mount the signs higher, away from the trucks' wind blasts, and made the supports stouter.
Illinois DOT also requires new overhead sign structures to be higher. I've noticed new ones are placed higher and that must be part of the reason why. Nice!
We had a problem in Virginia (and several other states) about a decade ago with the guardrails being too rigid. Instead of crumpling in a head-on collision and pushing the rail out of the way, the end of the guard rail stayed in place and went through the windshield and the driver's face. Lawsuits found the manufacturer had made an unapproved, undisclosed modification to the design before installation.
@@tvdan1043 I've seen a couple of videos of a guy checking guard rails and finding that they have been bolted/installed wrong. He explains why and then reports them to be remedied. TheGuardrailGuy. Installers don't always understand the thing they are installing.
@@gwaeron8630 yes, I read the guy is convinced his young daughter, while driving, died needlessly because she collided with a guardrail that was installed/repaired incorrectly. He’s been on a self imposed vendetta of sorts to expose the complex engineered guardrails need for competent installation….
Wow at 15:27 the tech specs on the TR1 damper are great. I expected the pneumatic stuff, but the inclusion of the magnet to create the eddy currents against the aluminum housing was just icing on the cake. Very impressive.
Mysteriously all 4 stoplights collapsed at an intersection right before I approached it in Cobb County, Georgia back in March. It was one of the strangest things I have ever seen.
Nebraska is the windiest state. Here in Omaha, larger intersections have diagonal trusses over the roadway that hold all the overhead signals and signs, similar to the single tube shown that goes over the road in the video, but lighter. 15:18 I've seen those on traffic signals here in Omaha. I had no idea what they were at first, and then decided that they had something to do to mitigate wind load. But I had no idea what they had inside them! Yay Valmont!!
We have those in a couple places in Kansas, too. The city of Lenexa added diagonal trusses along 87th Street Parkway (I know, pick one or the other, right) at the SPUI at I-35 and at the intersection with Renner Road, just west of I-435. And they're designed to be aesthetically pleasing, not just big aluminum tubes. The one at Renner is made in this curvy S-shape with little tails on the ends.
Yeah, I’ve seen one of the gantries on Dodge Street/US 6/Grand Army of the Republic Highway in person (not sure why we didn’t come in on I-680 like usual). They also have gantries like that at the SPUI’s with highway 77 in Lincoln (although they’re not diagonal)
There's another solution that wasn't mentioned, but which is applicable for any setting in which you have a non-traversable median. You can use a post-and-lintel mast arm arrangement. Rather than having a cantilever (arm fixed at one end, free at the other end), you can have it fixed at both ends. This reduces the degrees of freedom in which the mast arm can move, and it also negates the problem of uneven weight distribution inducing very intense loading at the mast arm's attachment point. It's not necessary to build a single extra large support structure, it's doable to build multiple smaller ones, likely at a lower overall cost and with fewer installation headaches.
Vortex shedding is the reason you see those spirals on tall, thin structures such as radar masts, industrial chimneys and old school car aerials. I'm guessing engineers had no success with the same here. Btw, note the corners on Teipei 101- they have a nice decorative cutout on each corner. This was actually designed later on in the process to address an issue with vortex shedding creating low pressure zones on the downwind side of the structure that were calculated to be strong enough to pull out windows. The cutouts on each corner disrupt the shedding to prevent these from forming, and the counterweight acts to stop the building moving unacceptably. Back to the signals, though - I wonder why not simply have a whole-road-width monotube? We have them holding up signs on the highway... If there's 2 upright components, the arm physically can't gallop
Here is a fantastic idea for a video. Road hazards that go unresolved or unnoticed. For example, on the George Washington Parkway in Virginia, just outside of Washington D.C., there is a stretch of road that has an almost glass-like road surface that becomes as slick and dangerous as black ice with even the slightest amount of moisture. Even high humidity turns this section into a skating rink. I used to drive a car with all wheel drive to work along that stretch and even with AWD and traction control I spun out more than once. Well, maybe not spun out, but I felt loss of traction and could have lost control with the wrong reaction or any kind of over correction. I've seen it happen to countless vehicles along that stretch. There are always accidents and pileups, almost every day. From Roosevelt Island to where it splits off to North Arlington, northbound, and the downhill curve heading in the other direction are both equally treacherous. Another road hazard that has caused numerous accidents but which is a permanent feature on another section of another road is a particular manhole cover that was installed improperly to begin with. But others become dangerous through improper maintenance or wear and tear/damage, etc. But the one I am talking about is on Lee highway in falls church, Virginia just before you get outside the beltway. It's after a long flat stretch of road just as you apex a right hand curve and begin to go up a hill. The manhole cover is perfectly lined up to be in the path of almost every tire of every vehicle in the right lane. The lip and rim of the cover is a good three or four inches above the road surface and the cover itself is recessed into the rim by about another four inches, creating a solid and unforgiving permanent pothole. Many of the accidents that are caused by this involve serious injuries and time consuming extractions. But the manhole cover appears to be well maintained as if VDOT is well aware of this pothole and actively maintains it. Ironically it's less than a quarter mile from a major VDOT equipment yard and state police refueling station.
I think our traffic poles in Australia mitigate this issue by having a single signal head that shows both straight and left turn movements in combination with stand alone vertical poles erected showing these movements. Probably costs less or the same as building one giant arm
Depending on how they're going about it, it might cost more just because running wires underground to more poles is a bit more complicated than just stringing them all together on the same pole. Well, for simpler intersections. Not having an entire set of lights for every lane would more than make up for that at multi-lane intersections, I think.
We also don't need a unique set of lights for every lane. If you have three lanes that will only ever move in unison (say, going straight) they'll all just share the one set of "going straight" lights. That way we don't need to get any lights into the middle of a huge intersection to begin with!
It's funny because there are some intersections, (mainly in Melbourne) that have 9 lights all in the same module, and one in the city that has 12, with a few extra beside them.
I just find it weird that the USA gives ever lane its own set of lights. Just... why? all the traffic going in the same direction will have the same light at the same time, after all. Where I live there's a main light for All traffic (repeated on ever corner and Sometimes a single overhead panel), and then secondary arrow lights May be present on that pannel as needed for each direction that traffic could be turning in. If you're in a lane that's turning in the indicated direction, the instruction given by the relevant arrow overrides the main light. It's very rare this amounts to more than two extra lights (because arrow lights are Only present when part of the cycle involves giving turning traffic Different instructions from everything else). Though in Theory a full array could amount to five columns (left most turning, less left turning, straight through/all, less right turning, right most turning, with a full red-amber-green set for each) or more (why does your intersection have more 6+ possible exits? WHY?! ), I'm fairly sure there's no intersection that actually does this.
Beat me to it. Seriously, that stroad he showed off in Vegas... 14 lanes of traffic! Did nobody stop to consider the absurdity of what they were doing, and that maybe there's a better solution to traffic than just throwing down more asphalt?
It's not just the insane width, it's the insistence that all that surface has to be devoted to Car alone. Can't have those signs and lights supported on both sides, because that would mean some place in the road where you can't make a U-turn! Obviously that Freedom must be prioritized over not having traffic lights fall on you.
I had no idea that 60-foot or 90-foot-long stoplights existed. That's simply terrifying. If a bird sat on one end, the leverage alone would put enormous loads on the structure. In my hometown, we often strung stoplights on cables suspended over wide roadways. This weighed less, and had the added advantage that because the stoplights themselves were only hung beneath the cable, they could simply swing out of the way of the wind. Of course, there was plenty of bouncing up and down, too, but it was less terrifying seeing a cable bounce than a stiff metal arm. However, they are now being replaced with more traditional stiff stoplights.
Those spirals you sometimes see at the top of tall chimneys are there to reduce vortex shedding. At the scale we're talking here, I wonder whether you could "just" wrap some thickish rubber insulation strip around the pole in a similar fashion.
I've noticed a bunch of moveable signs that have large circles cut out along the outside edge. I assumed that the purpose is to reduce the surface area that wind can exert twisting and/or tipping forces on.
In my other comment, I pointed out these were also present on older car aerials - so clearly this works on a small scale, too. I can only assume that this design was considered but not found to be effective.
I was wondering what those poles were. Just got new lights at an intersection here in Seattle (not tornado alley) and they have those dampers. But of course had no idea that what they were. Now I know. Woot!
Right at the end of your video, I went for the like button but realized I had already clicked it.. You're that good, Rob. Thank you for the entertainment :)
I've noticed that in some places, like North Carolina where I grew up, most of the traffic lights are simply hung from cables. In other places, like California where I live now, they're pretty much all mounted on poles like you show in this video. I have always wondered why some states use cables while others use poles.
I appreciate you correctly saying “Damper” and not “Dampener” (even though that schematic says “Wind Gallop ‘Dampening’ System) as the latter means to lightly moisten 😅
@@RoadGuyRob Yea, it’s interesting to me, I’ve become hyper aware of the word damper vs. dampener after I learned about dampers used on bikes. And as a Star Trek fan, I had to rewatch some clips of the crew saying jargon like “Inertial “Dampeners’” when in fact they should have said “Dampers” 😅
I would love to hear more about the kind that are just stoplights attached to a cable. I've seen those "gallop" in the wind and it honestly is more scary than when the poles do it.
About the part at 4:30, Canada has found a better solution for signal placements, where some of the left turn arrows are placed in the middle, concrete median of the roads.
Vortex shedding is reduced / eliminated on an automobile antenna (old style, not shark fin) by wrapping it with wire in a deep spiral - this could be done with power or signal cables, or with dedicated plastic or metal shapes.
Maybe we should just stop buidling roads so wide with intersections that take up so much sirface area that require us to re-engineer what should be simple things.
HAHA I love the Gorilla! We need more Gorillas in more videos everywhere!!! Also never thought about this issue! Fascinating that a stop sign galloping could cause so many issues.
Being from the UK it's always bizzar to see US traffic lights. We normally have just two to the left and right of the carriegway with maybe a third further along say on the roundabout or other side of the intersection then a turning signal mounted on the side of those if required. I remember in Germany seeing some larger poles that had signals for every lane but they were normally portal frame structures or had the cable to stop the bouncing.
Traffic engineers call these “traffic signals”. “Traffic light” and “stoplight” are taboo terms. But awesome research and great, precise information. I love your videos.
Last year in Las Vegas, the signals for westbound Flamingo Road at Fort Apache Road was brought down by a sudden wind storm. When replaced, the signal arm included the horizonal wind plates.
Where I live most traffic lights are on a cable strung between poles on each side of the street. They move some in wind but I've never seen one fall down and this must cheaper than using those big thick poles.
A majority of traffic lights in Minnesota, unlike the one shown in this video, are braced using a second smaller pole on the underside. Its always seemed like such a simple solution and I've always wondered why I only ever see it commonly in Minnesota.
It's not hard science to figure out the resonance frequency of a pole with lights on it. It's hard to predict it ahead of time, but, out in the real world it's dead simple. You grab the end, lift it a few inches, and drop it. It'll bob up and down like a sideways pendulum. You just measure it and now you know the frequency. Or, they make devices that can measure this to the millionth of a inch (strain gauges), you could put it anywhere on the post and have a reading within 2 seconds. Then you'd just tune the damper to that frequency. That said, the electromagnetic/pneumatic ones are universal and a better solution that tuning anyways.
I was thinking the same thing. You don't need to put the structure in a wind tunnel to find the natural frequency, since all that depends on, is the mass, distribution of mass, and stiffness of the pole. All that can be tested at ordinary wind speeds. Just put a strain gauge setup on the pole end, and apply a sample impulse load to the far end.
Love your videos, one thing I will give PA credit for (at least around Pittsburgh) is that when they replace older stop lights they are going for thicker / stronger structures. Everything from thicker poles to something that looks like the one on Decatur Blvd that you showed in Nevada. I only see those on the Pa turnpike for the most part and are typically painted blue!
I remember seeing this happening years ago, but wasn't sure whether it was safe or not--luckily enough, it at least didn't fall down while I was in the area. I did wonder how it happened, but it's been a long time since I've seen it happening, so I haven't been thinking about it.
I've seen some places hold these up on both sides, either by being double the length or if there's a median strip, put the other pole in the middle. The example at 6:00 is the beefier sort but I think being held on both ends also help.
Seems like a bar going all the way across is ur answer. He mentions the expense of it. When u add in the cost of the maintenance of half street arms, seems like full street is less headache
Makes me think we need to work on our roads- maybe make them with less lanes, and have have a 2-3 short, vertical lights on each side of intersections instead. Would probably also make people focus more on the road and their surroundings this way too
Год назад+1
They could also try to simply put very thick robe wrapped around the arm. More robust option is to weld metal strip that is wrapping around it. As you mentioned, this issue mostly comes from the vortex that has frequency and strength that depends on the wind (and post thickness). Now if you wrap something around the post arm, it's not round anymore! Of course strong wind can still bounce it around but the most important part is that fairly constant wind will not cause galloping. Let's say that you wrap around every 3 feet. This means that every 1,5 feet the extruding part will be on the opposite side of the arm and it sort of acts as a sail. Except the direction is the opposite every 1,5 feet. It will still resonate but instead of having one 20 feet arm resonating, you have lots of 3 feet peaces that resonate independently with much smaller amplitude. And what happens when resonance amplitude goes down? The resonance frequency goes up a lot! I have no clue how this method is called but it exists and it is used in many applications. I've seen it mostly on industrial chimneys that are very tall, round and made out of fairly thin steel for their size. They love to sway back and forth and even worse, the wind can blow from any direction! Yet, it's enough that there is metal band that wraps around it a few times to change the resonance frequency way outside of what wind can do.
this really has the quality of golden age myth busters / TV on discovery. Something to put on and just learn something interesting and get yourself thinking.
Big thing in Colorado as well, can't count how many times I've been driving and seen traffic lights doing the wind dance, some of them are strung up by some time of wire and I may not be a structural engineer but those ones usually swing around a lot more than the poles but those poles are a lot more scary to watch Bob up and down and all around
Fun fact: This isn't directly related, but if you're in the woods, you can actually topple trees with the right amount of effort, pushing on the trunk until you get the top of the tree really swaying hard until the load becomes too much for the roots to hold, or it might just snap off. Works best on older/dead trees.
The person that pulled up to the intersection at the very end of the video looked like they were thinking of turning right at first, but saw some inarguably weird stuff happening and said, "screw that" and turned left in a hurry.
Awesome video as usual! I Love these! Always was fascinated with traffic signal set up’s! I constructed a half scale span wire set up with two real signals in my back yard!
They put these noncounterbalenced monstrosities in my town and one fell over and blocked fire trucks from going one direction for three hours ! And it almost crushed people who were standing on the sidewalk .
As a kid growing up in the Bay Area of California, I've seen several kinds of different traffic signal setups at many intersections. One that stood out to me was that California at one time was big at installing left turn signals using mast arms shaped like a "T" on the median. That made it possible to mount more than one signal on the mast. As a kid, I thought it was a cool thing to see. As an adult, it makes more sense. That kind of installation allowed for shorter mast arms while providing signal coverage for the intersection. That right there was one way to reduce galloping on the mast arm. For more windy locations, I wonder to myself why they don't adopt a similar practice. There is one drawback, though. Someone who isn't watching where they're going can crash into it and knock the signal down. With all that said, that's one way traffic engineers can reduce galloping on the mast arm.
Wind blowing on the face of the stop lights, because they're not mounted in the middle, causes a torsion on the horizontal span of the pole, and because that energy has to go somewhere, it causes the up and down osculation. In Alberta and Saskatchewan, a lot of stop lights are mounted horizontally, to reduce the torsion the winds create on the poles.
There is an entire field of study dedicated to the interactions between the aerodynamic loads and the resulting structural deformations: it's called aeroelasticity. 95% of all the “aeroelasticians” of this world work in aerospace (from research lab at universities to companies like Airbus and Boeing). Of course similar interactions happen to many other man made objects such as bridges (see the Tacoma bridge disaster), wind turbines, solar panels, sailing hydrofoils and of course traffic signals. Thanks for covering this topic!
This is the same characteristic that makes suspension bridge wires vibrate and smoke stacks sway. And the same fixes work for it, a spiral fin on the tubular form will cause it to shed vortexes.
You can also stop the motion by controlling the vortex shedding. Some car antennas and smokestacks will use helical strakes that help control the vortex shedding to the point you don't need a damper.
A problem that only exists because of suboptimal intersection design. In Germany we usually just split up the lanes and add traffic isles with more poles.
in tampa bay the vast majority of major stoplights and highway signs are built like that huge nevada one. i always assumed it was for hurricanes, but good to know that it's just safer in general too
The hood on the light is open on the bottom,. so the light would receive a vertical thrust at every gust. That would induce an oscillation as the gusts alternately lift and drop the heads.
RGR, love your videos! I wonder if mounting the lights on just a short sign or light pole would help with wind induced motion. Of course the downside is that it might be harder for drivers to see.
There is a city about 4 or 5 hours east of me that does this -- it is much harder to tell what is going on at an intersection safely. I think they actually did this as an over-compensation for removing all the overhead wires that used to fill the sky over the streets there.
I was hoping dampers would come up during the video, but was envisioning some kind of rubber mounting pad between the pole and arm. The damping rod that just bolts to the pole is certainly easier to install and won't degrade over time the way rubber will, but man that sure seems expensive for what doesn't really look like that complicated or expensive a device to manufacture.
Wow, a major problem indeed. It’s almost like the solution is as simple as having 1 pole on either side and having them all joined with a longer arch. Oh wait, yeah that would solve all the problems here 😑
If you want to find out about one of the most dramatic incidents of resonance induced (via vortex shedding), structural failures Google the Tacoma Narrows bridge failure. The mechanisms are similar to what you're talking about here.
I saw a video of a traffic light arm in Punta Gorda going crazy during hurricane Ian,it didn't come down but it would have almost certainly caused significant damage. 🌀🚦
A cross bar where the vertical meets the horizontal would stiffen this up massively. It would only need to be about 10 feet out at most and connect at the same distance down. Triangles are the stiffest structure.
My town replaced all the old cable-suspended stoplights but replaced them with these more unreliable cantilever poles. The old ones almost never failed, unless in hurricane high winds which seem to break the new poles just as much anyway. Also I imagine a cable is cheaper to replace than a large steel pipe.
My solution. Central reservations and set back stop line. Have it so you have the left turn light on the central reservation then straight come from the right. You shorten the arm while still allowing over hight vehicles to go around
Those traffic lights look flimsy compared to the ones we have here in Australia. I am referring to the over-hang type. All the ones here are made of heavy galvanised RHS (Rectangular hollow section) with a base plate of at lease 30mm steel. They are build tough.
Have the dampener and a horizontal solar panel. Maybe together they can cancel out resonance and supply excess electricity to run the lights or at least power a backup battery in case of a power outage.
My initial thought was why not just have the lights have two legs like the gantry at 5:55. _That_ one is expensive overkill, but it seems like you could easily make one out of the thinner poles and have them be just as effective. You'd also use less metal for one big diagonal signal instead of four perpendicular signals, so it's stronger _and_ cheaper.
I love road guy rob’s videos. Unlike some other road and urbanists channels imo he certainly presents videos and information in a way that is informative and entertaining!
Another idea I just had was that maybe they should cross brace the pole and the cantilever part in some way, kind of like how buildings are braced to withstand earthquakes. I mean wind is kind of different because it's hitting the entire side, whereas the earthquake is more like pulling the rug out from underneath a structure repeatedly but surely some of the same things apply.
If you want to learn the resonance of a cantilever (even with stuff on it), you just go up and twang it and measure it. Then you go back to the shop cut a spring to the right length to make a tuned dampener and put it in a cylinder with a cannon ball on top of it to make a tuned dampener, then you go back and put it on the arm. Just three components and the cost of going back to bolt it on.
No mention of fitting helixes to the structure? Is that too expensive or technical to do as it's a non moving part that would require little to no maintenance.
On the campus of the hospital I work at, they have a sign maintenance contractor who installs and maintains the road signs and striping. In the last few months they've replaced some of the moveable/temporary signs with versions that have large holes cut into the metal facing. It is obviously intended to reduce the amount of surface that wind can exert force on to lessen tipping over and twisting. The stop signs near one construction entrance have a coffee cup sized hole cut into each corner along the outside edge. I have been trying to imagine the change in force that removing that amount of surface area causes or whether they cut those holes in that particular configuration simply for aesthetics/symmetry, but I don't know all that much about wind sheer to get even a basic model constructed in my mind. Lol.
We have this issue in Canada too. It's quite remarkable how much abuse these things handle. I've collected quite a few heads on the behalf of the local utility during major windstorms.
Road guy rob! I love your videos. Unlike most educational videos you actual go to the source and film in the field rather than doing it all with voice over and stock videos and photos. I really appreciate all the work you do for your channel. Keep up the great work!
Exactly!
Thank you! It's very time consuming. Glad to hear it's worth the effort!
@@RoadGuyRob You're a very unique channel on the internet, which is saying something! Keep up the great work!
Love and respect from Nebraska!
@@RoadGuyRob i love your videos more than Not Just bikes’ videos. You present information in an interesting way that is entertaining and less “wah” moment than some urbanist channels.
@@charlesrodriguez7984 He offers a moral destination to walk towards.
I focus on the first steps cities/states can take on the journey.
It's not just natural wind. Back in the '90s New York's DOT found an overhead sign structure that was bouncing every time a truck went under it. They inspected it and found it was starting to crack.
If I recall right, they changef their design standards to mount the signs higher, away from the trucks' wind blasts, and made the supports stouter.
The damper in the video addresses trucks going under it. Thats interesting
Illinois DOT also requires new overhead sign structures to be higher. I've noticed new ones are placed higher and that must be part of the reason why. Nice!
Rob on a swing set being pushed by a gorilla. This makes my day.
Great content about the wind vortices and how they work against the poles.
All the kids disappeared when their moms saw that strange scene
The wind vortices/resonance frequency were actually my first thought as to why it was happening; I'm not a genius, I just like physics :p
Would love it if you did a video on guardrail and guardrail types next and why certain types are used in certain spots of roads and freeways.
Yes it does appear There's a lot of technology on the guard rail end caps.
We had a problem in Virginia (and several other states) about a decade ago with the guardrails being too rigid. Instead of crumpling in a head-on collision and pushing the rail out of the way, the end of the guard rail stayed in place and went through the windshield and the driver's face. Lawsuits found the manufacturer had made an unapproved, undisclosed modification to the design before installation.
@@tvdan1043 I've seen a couple of videos of a guy checking guard rails and finding that they have been bolted/installed wrong. He explains why and then reports them to be remedied. TheGuardrailGuy. Installers don't always understand the thing they are installing.
@@gwaeron8630 yes, I read the guy is convinced his young daughter, while driving, died needlessly because she collided with a guardrail that was installed/repaired incorrectly. He’s been on a self imposed vendetta of sorts to expose the complex engineered guardrails need for competent installation….
Andrew Lam has a good video on road barriers including guard rails.
Wow at 15:27 the tech specs on the TR1 damper are great. I expected the pneumatic stuff, but the inclusion of the magnet to create the eddy currents against the aluminum housing was just icing on the cake. Very impressive.
Yeah... Totally was thinking the same thing...
And Valmont is less than 10 miles from me, here in Eastern Nebraska, just NW of Omaha.
They are working on other dampers for street/area light poles as well. Really cool stuff.
Completely passive, and very little maintenance!
I want to point out that @thisoldtony has a good video on rotary and linear dampers for anyone interested in more information
Mysteriously all 4 stoplights collapsed at an intersection right before I approached it in Cobb County, Georgia back in March. It was one of the strangest things I have ever seen.
That is odd. Sinkhole maybe???
Final destination stuff there.
Where at?? I live in Cobb myself!!
@@thewindowisrusty the intersection of Busbee and Barrett Pkwy. Wsbtv did a story on it. Very odd.
@@guriausa Oh wow. That is one heck of an intersection for that to happen in. I am on the Austell side of Cobb, but even I know where that is!
Nebraska is the windiest state.
Here in Omaha, larger intersections have diagonal trusses over the roadway that hold all the overhead signals and signs, similar to the single tube shown that goes over the road in the video, but lighter.
15:18 I've seen those on traffic signals here in Omaha. I had no idea what they were at first, and then decided that they had something to do to mitigate wind load. But I had no idea what they had inside them! Yay Valmont!!
We have those in a couple places in Kansas, too. The city of Lenexa added diagonal trusses along 87th Street Parkway (I know, pick one or the other, right) at the SPUI at I-35 and at the intersection with Renner Road, just west of I-435. And they're designed to be aesthetically pleasing, not just big aluminum tubes. The one at Renner is made in this curvy S-shape with little tails on the ends.
We have some in Texas too. I don’t know how they aren’t where I live considering I live in the 3rd windiest city in the US.
Cool, sounds steampunk AF.
Also I'd bet that a truss, with all its crazy angles, doesn't suffer from vortex shedding that a straight pole does.
Yeah, I’ve seen one of the gantries on Dodge Street/US 6/Grand Army of the Republic Highway in person (not sure why we didn’t come in on I-680 like usual). They also have gantries like that at the SPUI’s with highway 77 in Lincoln (although they’re not diagonal)
There's another solution that wasn't mentioned, but which is applicable for any setting in which you have a non-traversable median. You can use a post-and-lintel mast arm arrangement. Rather than having a cantilever (arm fixed at one end, free at the other end), you can have it fixed at both ends. This reduces the degrees of freedom in which the mast arm can move, and it also negates the problem of uneven weight distribution inducing very intense loading at the mast arm's attachment point. It's not necessary to build a single extra large support structure, it's doable to build multiple smaller ones, likely at a lower overall cost and with fewer installation headaches.
I did wonder this as well - particularly as this was the design chosen for the intersection featured with that 200' span.
Vortex shedding is the reason you see those spirals on tall, thin structures such as radar masts, industrial chimneys and old school car aerials. I'm guessing engineers had no success with the same here.
Btw, note the corners on Teipei 101- they have a nice decorative cutout on each corner. This was actually designed later on in the process to address an issue with vortex shedding creating low pressure zones on the downwind side of the structure that were calculated to be strong enough to pull out windows. The cutouts on each corner disrupt the shedding to prevent these from forming, and the counterweight acts to stop the building moving unacceptably.
Back to the signals, though - I wonder why not simply have a whole-road-width monotube? We have them holding up signs on the highway... If there's 2 upright components, the arm physically can't gallop
Coming in late on this, they're called helical strakes and it could be that they just didn't think about using them on horizontal structures.
Here is a fantastic idea for a video. Road hazards that go unresolved or unnoticed.
For example, on the George Washington Parkway in Virginia, just outside of Washington D.C., there is a stretch of road that has an almost glass-like road surface that becomes as slick and dangerous as black ice with even the slightest amount of moisture. Even high humidity turns this section into a skating rink. I used to drive a car with all wheel drive to work along that stretch and even with AWD and traction control I spun out more than once. Well, maybe not spun out, but I felt loss of traction and could have lost control with the wrong reaction or any kind of over correction. I've seen it happen to countless vehicles along that stretch. There are always accidents and pileups, almost every day. From Roosevelt Island to where it splits off to North Arlington, northbound, and the downhill curve heading in the other direction are both equally treacherous.
Another road hazard that has caused numerous accidents but which is a permanent feature on another section of another road is a particular manhole cover that was installed improperly to begin with. But others become dangerous through improper maintenance or wear and tear/damage, etc. But the one I am talking about is on Lee highway in falls church, Virginia just before you get outside the beltway. It's after a long flat stretch of road just as you apex a right hand curve and begin to go up a hill. The manhole cover is perfectly lined up to be in the path of almost every tire of every vehicle in the right lane. The lip and rim of the cover is a good three or four inches above the road surface and the cover itself is recessed into the rim by about another four inches, creating a solid and unforgiving permanent pothole.
Many of the accidents that are caused by this involve serious injuries and time consuming extractions. But the manhole cover appears to be well maintained as if VDOT is well aware of this pothole and actively maintains it. Ironically it's less than a quarter mile from a major VDOT equipment yard and state police refueling station.
NoVA resident here. I think you're talking about RT 29 (Lee Hwy) near the I-495 Express Lane exit, but before the Shreve RD intersection/light? 🤔
I think our traffic poles in Australia mitigate this issue by having a single signal head that shows both straight and left turn movements in combination with stand alone vertical poles erected showing these movements. Probably costs less or the same as building one giant arm
Depending on how they're going about it, it might cost more just because running wires underground to more poles is a bit more complicated than just stringing them all together on the same pole. Well, for simpler intersections. Not having an entire set of lights for every lane would more than make up for that at multi-lane intersections, I think.
We also don't need a unique set of lights for every lane. If you have three lanes that will only ever move in unison (say, going straight) they'll all just share the one set of "going straight" lights. That way we don't need to get any lights into the middle of a huge intersection to begin with!
@@laurencefraser that'd require critical thinking skills
It's funny because there are some intersections, (mainly in Melbourne) that have 9 lights all in the same module, and one in the city that has 12, with a few extra beside them.
"Not cheap" at $6k? FOR FOUR?!?! Are you kidding me? That's dirt cheap in road infrastructure spending.
Ridiculous that we have such wide stroads.
I just find it weird that the USA gives ever lane its own set of lights. Just... why? all the traffic going in the same direction will have the same light at the same time, after all.
Where I live there's a main light for All traffic (repeated on ever corner and Sometimes a single overhead panel), and then secondary arrow lights May be present on that pannel as needed for each direction that traffic could be turning in. If you're in a lane that's turning in the indicated direction, the instruction given by the relevant arrow overrides the main light. It's very rare this amounts to more than two extra lights (because arrow lights are Only present when part of the cycle involves giving turning traffic Different instructions from everything else). Though in Theory a full array could amount to five columns (left most turning, less left turning, straight through/all, less right turning, right most turning, with a full red-amber-green set for each) or more (why does your intersection have more 6+ possible exits? WHY?! ), I'm fairly sure there's no intersection that actually does this.
@@laurencefraser It's not weird, it's safer. It's also not everywhere in the US.
Tom Dees
1 second ago
so...what type of "stroads" do you suggest, and dealing with the congestion that would entail 🤣
Beat me to it. Seriously, that stroad he showed off in Vegas... 14 lanes of traffic! Did nobody stop to consider the absurdity of what they were doing, and that maybe there's a better solution to traffic than just throwing down more asphalt?
It's not just the insane width, it's the insistence that all that surface has to be devoted to Car alone. Can't have those signs and lights supported on both sides, because that would mean some place in the road where you can't make a U-turn! Obviously that Freedom must be prioritized over not having traffic lights fall on you.
You could see in his expression that Carl from Valmont clearly loves his job - even as much as Road Guy Rob!
I had no idea that 60-foot or 90-foot-long stoplights existed. That's simply terrifying. If a bird sat on one end, the leverage alone would put enormous loads on the structure. In my hometown, we often strung stoplights on cables suspended over wide roadways. This weighed less, and had the added advantage that because the stoplights themselves were only hung beneath the cable, they could simply swing out of the way of the wind. Of course, there was plenty of bouncing up and down, too, but it was less terrifying seeing a cable bounce than a stiff metal arm. However, they are now being replaced with more traditional stiff stoplights.
Those spirals you sometimes see at the top of tall chimneys are there to reduce vortex shedding. At the scale we're talking here, I wonder whether you could "just" wrap some thickish rubber insulation strip around the pole in a similar fashion.
I've noticed a bunch of moveable signs that have large circles cut out along the outside edge. I assumed that the purpose is to reduce the surface area that wind can exert twisting and/or tipping forces on.
In my other comment, I pointed out these were also present on older car aerials - so clearly this works on a small scale, too. I can only assume that this design was considered but not found to be effective.
I was wondering what those poles were. Just got new lights at an intersection here in Seattle (not tornado alley) and they have those dampers. But of course had no idea that what they were. Now I know. Woot!
Right at the end of your video, I went for the like button but realized I had already clicked it.. You're that good, Rob. Thank you for the entertainment :)
I've noticed that in some places, like North Carolina where I grew up, most of the traffic lights are simply hung from cables. In other places, like California where I live now, they're pretty much all mounted on poles like you show in this video. I have always wondered why some states use cables while others use poles.
I appreciate you correctly saying “Damper” and not “Dampener” (even though that schematic says “Wind Gallop ‘Dampening’ System) as the latter means to lightly moisten 😅
I had to fact check that. The words are easy to mix up!
@@RoadGuyRob Yea, it’s interesting to me, I’ve become hyper aware of the word damper vs. dampener after I learned about dampers used on bikes. And as a Star Trek fan, I had to rewatch some clips of the crew saying jargon like “Inertial “Dampeners’” when in fact they should have said “Dampers” 😅
I would love to hear more about the kind that are just stoplights attached to a cable. I've seen those "gallop" in the wind and it honestly is more scary than when the poles do it.
About the part at 4:30, Canada has found a better solution for signal placements, where some of the left turn arrows are placed in the middle, concrete median of the roads.
Yeah I see an awful lack of refuge islands/medians, adding them would also make crossing the street a lot safer for pedestrians.
12:27 Now I'm wondering what the natural frequency of Big Bird is...
Finally, I get an answer how to pronounce Tooele! Will Road Guy Rob's miracles never cease??!?!
Vortex shedding is reduced / eliminated on an automobile antenna (old style, not shark fin) by wrapping it with wire in a deep spiral - this could be done with power or signal cables, or with dedicated plastic or metal shapes.
Maybe we should just stop buidling roads so wide with intersections that take up so much sirface area that require us to re-engineer what should be simple things.
HAHA I love the Gorilla! We need more Gorillas in more videos everywhere!!! Also never thought about this issue! Fascinating that a stop sign galloping could cause so many issues.
Being from the UK it's always bizzar to see US traffic lights. We normally have just two to the left and right of the carriegway with maybe a third further along say on the roundabout or other side of the intersection then a turning signal mounted on the side of those if required. I remember in Germany seeing some larger poles that had signals for every lane but they were normally portal frame structures or had the cable to stop the bouncing.
Traffic engineers call these “traffic signals”. “Traffic light” and “stoplight” are taboo terms.
But awesome research and great, precise information. I love your videos.
Last year in Las Vegas, the signals for westbound Flamingo Road at Fort Apache Road was brought down by a sudden wind storm. When replaced, the signal arm included the horizonal wind plates.
Where I live most traffic lights are on a cable strung between poles on each side of the street. They move some in wind but I've never seen one fall down and this must cheaper than using those big thick poles.
Really realistic stoplight model! Never turns green the entire video!
A majority of traffic lights in Minnesota, unlike the one shown in this video, are braced using a second smaller pole on the underside. Its always seemed like such a simple solution and I've always wondered why I only ever see it commonly in Minnesota.
This is the first video of yours i have watched, and i was surprised as heck to see the intersections right by my house featured.
It's not hard science to figure out the resonance frequency of a pole with lights on it. It's hard to predict it ahead of time, but, out in the real world it's dead simple. You grab the end, lift it a few inches, and drop it. It'll bob up and down like a sideways pendulum. You just measure it and now you know the frequency. Or, they make devices that can measure this to the millionth of a inch (strain gauges), you could put it anywhere on the post and have a reading within 2 seconds. Then you'd just tune the damper to that frequency. That said, the electromagnetic/pneumatic ones are universal and a better solution that tuning anyways.
thought so too, but you'd have to add retuning to maintenance schedule.
I was thinking the same thing. You don't need to put the structure in a wind tunnel to find the natural frequency, since all that depends on, is the mass, distribution of mass, and stiffness of the pole. All that can be tested at ordinary wind speeds. Just put a strain gauge setup on the pole end, and apply a sample impulse load to the far end.
Love your videos, one thing I will give PA credit for (at least around Pittsburgh) is that when they replace older stop lights they are going for thicker / stronger structures. Everything from thicker poles to something that looks like the one on Decatur Blvd that you showed in Nevada. I only see those on the Pa turnpike for the most part and are typically painted blue!
6:54 This one is not easy to hug, it's easy to strangle.
I remember seeing this happening years ago, but wasn't sure whether it was safe or not--luckily enough, it at least didn't fall down while I was in the area. I did wonder how it happened, but it's been a long time since I've seen it happening, so I haven't been thinking about it.
I always enjoy all the stock photos in Lubbock, Texas. Rob must really love us, ha.
I've seen some places hold these up on both sides, either by being double the length or if there's a median strip, put the other pole in the middle. The example at 6:00 is the beefier sort but I think being held on both ends also help.
Seems like a bar going all the way across is ur answer. He mentions the expense of it. When u add in the cost of the maintenance of half street arms, seems like full street is less headache
Makes me think we need to work on our roads- maybe make them with less lanes, and have have a 2-3 short, vertical lights on each side of intersections instead. Would probably also make people focus more on the road and their surroundings this way too
They could also try to simply put very thick robe wrapped around the arm. More robust option is to weld metal strip that is wrapping around it. As you mentioned, this issue mostly comes from the vortex that has frequency and strength that depends on the wind (and post thickness). Now if you wrap something around the post arm, it's not round anymore! Of course strong wind can still bounce it around but the most important part is that fairly constant wind will not cause galloping. Let's say that you wrap around every 3 feet. This means that every 1,5 feet the extruding part will be on the opposite side of the arm and it sort of acts as a sail. Except the direction is the opposite every 1,5 feet. It will still resonate but instead of having one 20 feet arm resonating, you have lots of 3 feet peaces that resonate independently with much smaller amplitude. And what happens when resonance amplitude goes down? The resonance frequency goes up a lot!
I have no clue how this method is called but it exists and it is used in many applications. I've seen it mostly on industrial chimneys that are very tall, round and made out of fairly thin steel for their size. They love to sway back and forth and even worse, the wind can blow from any direction! Yet, it's enough that there is metal band that wraps around it a few times to change the resonance frequency way outside of what wind can do.
this really has the quality of golden age myth busters / TV on discovery. Something to put on and just learn something interesting and get yourself thinking.
Your videos are next level, love them so much!
At 6:00 my European brain aches looking at all that expensive infrastructure for an intersection that would be perfect for a simple roundabout
Nice of them to include a bike lane too 😬
I've noticed these vertical pipes at the end poles, nice to know of their function.
Big thing in Colorado as well, can't count how many times I've been driving and seen traffic lights doing the wind dance, some of them are strung up by some time of wire and I may not be a structural engineer but those ones usually swing around a lot more than the poles but those poles are a lot more scary to watch Bob up and down and all around
Those stop light clusters are friggin big too. A stack of 3 , red, yellow, green is like 6 feet tall, and 2.5 feet wide.
Yeah, Rob, did you know that the church has been installing tuned mass dampers in the Salt Lake Temple during this huge renovation project?
Fun fact: This isn't directly related, but if you're in the woods, you can actually topple trees with the right amount of effort, pushing on the trunk until you get the top of the tree really swaying hard until the load becomes too much for the roots to hold, or it might just snap off. Works best on older/dead trees.
The vid was definitely worth the wait Rob, keep up the good vids we love it
Thank you
I've wondered what those things are for! Terrific presentation. Thanks
The person that pulled up to the intersection at the very end of the video looked like they were thinking of turning right at first, but saw some inarguably weird stuff happening and said, "screw that" and turned left in a hurry.
Awesome video as usual! I Love these! Always was fascinated with traffic signal set up’s! I constructed a half scale span wire set up with two real signals in my back yard!
I'm from the new Orleans area. I've never seen traffic lights gallop as serious as shown in this video
They put these noncounterbalenced monstrosities in my town and one fell over and blocked fire trucks from going one direction for three hours ! And it almost crushed people who were standing on the sidewalk .
As a kid growing up in the Bay Area of California, I've seen several kinds of different traffic signal setups at many intersections. One that stood out to me was that California at one time was big at installing left turn signals using mast arms shaped like a "T" on the median. That made it possible to mount more than one signal on the mast. As a kid, I thought it was a cool thing to see. As an adult, it makes more sense. That kind of installation allowed for shorter mast arms while providing signal coverage for the intersection. That right there was one way to reduce galloping on the mast arm. For more windy locations, I wonder to myself why they don't adopt a similar practice. There is one drawback, though. Someone who isn't watching where they're going can crash into it and knock the signal down. With all that said, that's one way traffic engineers can reduce galloping on the mast arm.
Wind blowing on the face of the stop lights, because they're not mounted in the middle, causes a torsion on the horizontal span of the pole, and because that energy has to go somewhere, it causes the up and down osculation. In Alberta and Saskatchewan, a lot of stop lights are mounted horizontally, to reduce the torsion the winds create on the poles.
There is an entire field of study dedicated to the interactions between the aerodynamic loads and the resulting structural deformations: it's called aeroelasticity. 95% of all the “aeroelasticians” of this world work in aerospace (from research lab at universities to companies like Airbus and Boeing). Of course similar interactions happen to many other man made objects such as bridges (see the Tacoma bridge disaster), wind turbines, solar panels, sailing hydrofoils and of course traffic signals. Thanks for covering this topic!
I see those bobbing up and down ALL the time in wind around here during storms...always wondered how they manage to keep them from failing.
In the UK, Storm Enuice last year twisted some traffic lights but didn't make them collapse.
Wow this is amazing!!! Shout out to the guy who created this!!! This can make a big difference!
I live in Utah and have seen these all over and always wondered what they were. I asumed they were weather related but I now know.
It's satisfying watching it wobble, but I also know it could fall if it does to much wobble
Was hoping to see mention of span wire traffic signals.
This is the same characteristic that makes suspension bridge wires vibrate and smoke stacks sway. And the same fixes work for it, a spiral fin on the tubular form will cause it to shed vortexes.
You can also stop the motion by controlling the vortex shedding. Some car antennas and smokestacks will use helical strakes that help control the vortex shedding to the point you don't need a damper.
A problem that only exists because of suboptimal intersection design. In Germany we usually just split up the lanes and add traffic isles with more poles.
in tampa bay the vast majority of major stoplights and highway signs are built like that huge nevada one. i always assumed it was for hurricanes, but good to know that it's just safer in general too
15:12 when I first saw those I thought they were transmitters but I learned what they were because of a UDOT manual
Boy, these engineers ain't horsing around unlike those pole arms!
P.S. How much is the rate for appearing in a RGR video in a gorilla suit?
The hood on the light is open on the bottom,. so the light would receive a vertical thrust at every gust. That would induce an oscillation as the gusts alternately lift and drop the heads.
RGR, love your videos! I wonder if mounting the lights on just a short sign or light pole would help with wind induced motion. Of course the downside is that it might be harder for drivers to see.
There is a city about 4 or 5 hours east of me that does this -- it is much harder to tell what is going on at an intersection safely. I think they actually did this as an over-compensation for removing all the overhead wires that used to fill the sky over the streets there.
oh boy vortex shedding! my favorite!
I was hoping dampers would come up during the video, but was envisioning some kind of rubber mounting pad between the pole and arm. The damping rod that just bolts to the pole is certainly easier to install and won't degrade over time the way rubber will, but man that sure seems expensive for what doesn't really look like that complicated or expensive a device to manufacture.
Wow, a major problem indeed. It’s almost like the solution is as simple as having 1 pole on either side and having them all joined with a longer arch. Oh wait, yeah that would solve all the problems here 😑
In Germany I see this solution everywhere. Seems like it is an American only problem...
If you want to find out about one of the most dramatic incidents of resonance induced (via vortex shedding), structural failures Google the Tacoma Narrows bridge failure. The mechanisms are similar to what you're talking about here.
I saw a video of a traffic light arm in Punta Gorda going crazy during hurricane Ian,it didn't come down but it would have almost certainly caused significant damage.
🌀🚦
A cross bar where the vertical meets the horizontal would stiffen this up massively. It would only need to be about 10 feet out at most and connect at the same distance down. Triangles are the stiffest structure.
My town replaced all the old cable-suspended stoplights but replaced them with these more unreliable cantilever poles. The old ones almost never failed, unless in hurricane high winds which seem to break the new poles just as much anyway. Also I imagine a cable is cheaper to replace than a large steel pipe.
To be fare they are larger than the poles shown in this video and are hexagon shaped which should help with rigidity
I was wondering what a vertical pole was doing on a new stoplight. Now I know! Thx Rob!
The hanging ball on a coil spring has been used on some pipelines in the Alaskan North Slope oilfield for about 40 years.
My solution. Central reservations and set back stop line. Have it so you have the left turn light on the central reservation then straight come from the right. You shorten the arm while still allowing over hight vehicles to go around
Those traffic lights look flimsy compared to the ones we have here in Australia.
I am referring to the over-hang type. All the ones here are made of heavy galvanised RHS (Rectangular hollow section) with a base plate of at lease 30mm steel.
They are build tough.
Have the dampener and a horizontal solar panel. Maybe together they can cancel out resonance and supply excess electricity to run the lights or at least power a backup battery in case of a power outage.
My initial thought was why not just have the lights have two legs like the gantry at 5:55. _That_ one is expensive overkill, but it seems like you could easily make one out of the thinner poles and have them be just as effective. You'd also use less metal for one big diagonal signal instead of four perpendicular signals, so it's stronger _and_ cheaper.
We make them with trusses, typically supported on both sides. These giant horizontal pipes are weird.
I love road guy rob’s videos. Unlike some other road and urbanists channels imo he certainly presents videos and information in a way that is informative and entertaining!
This channel needs to be nominated for the RUclips Video Awards. No, seriously.
using eddie currents as a damper is pretty genious
engineering is so cool. Really wish stuff was like this was taught in school.
Another idea I just had was that maybe they should cross brace the pole and the cantilever part in some way, kind of like how buildings are braced to withstand earthquakes. I mean wind is kind of different because it's hitting the entire side, whereas the earthquake is more like pulling the rug out from underneath a structure repeatedly but surely some of the same things apply.
If you want to learn the resonance of a cantilever (even with stuff on it), you just go up and twang it and measure it. Then you go back to the shop cut a spring to the right length to make a tuned dampener and put it in a cylinder with a cannon ball on top of it to make a tuned dampener, then you go back and put it on the arm.
Just three components and the cost of going back to bolt it on.
I've never seen this problem, but then in the UK I've never seen this bad light design used. Interesting to see though, cheers
I was wondering when Galloping Gertie was going to be mentioned.
always good to see a video from rob
No mention of fitting helixes to the structure? Is that too expensive or technical to do as it's a non moving part that would require little to no maintenance.
On the campus of the hospital I work at, they have a sign maintenance contractor who installs and maintains the road signs and striping. In the last few months they've replaced some of the moveable/temporary signs with versions that have large holes cut into the metal facing. It is obviously intended to reduce the amount of surface that wind can exert force on to lessen tipping over and twisting. The stop signs near one construction entrance have a coffee cup sized hole cut into each corner along the outside edge. I have been trying to imagine the change in force that removing that amount of surface area causes or whether they cut those holes in that particular configuration simply for aesthetics/symmetry, but I don't know all that much about wind sheer to get even a basic model constructed in my mind. Lol.
We have this issue in Canada too. It's quite remarkable how much abuse these things handle. I've collected quite a few heads on the behalf of the local utility during major windstorms.
In Orlando some of the intersections have a square for the lights