Basics of Concrete Barriers (2000)

https://highways.dot.gov/public-roads/marchapril-2000/basics-concrete-barriers

by quotha • 4 years ago

137 80 4 years ago

highways.dot.gov

ggm• 4 years ago

Amazingly well thought out design. If you want something as impactful (hah) think about the fluid related mechanics of urinal and toilet design, and how much thought has to go into splashback.

Jersey kerb has become ubiquitous worldwide.

Interestingly, the alternate designs often used (guyed wires, steel barrier) have good and bad points, for survivability if an impact is unavoidable. They "give" -and in some circumstances, thats exactly what you want. Jersey Kerb is for the "nope: no giving here: wear the decelleration, hard" situations where giving (eg. into the oncoming traffic flow) would be worse overall.

TedDoesntTalk• 4 years ago

splashback

I thought that is what the plastic filters at the bottom assisted with

halpmeh• 4 years ago

They do, but well designed urinals have very little splash back even without the plastic filter.

abestic9• 4 years ago

If you're having trouble reading the diagrams, several barrier types are available in this New Zealand Transport Agency publication [1]. The F-shape barrier is detailed on page 10.

[1] https://arco.co.nz/wp-content/uploads/2017/12/m23-road-safet...

anonu• 4 years ago

Really cool. Is it just me or are metal wire barriers not very common in US road designs. They seem to be quite popular in Europe.

irjustin• 4 years ago

Wire barriers are more common outside of city, urban areas where you start getting into long stretches without much else[0].

Of course they're cheap and easy to install, but their main downsides are, having a higher rate of killing those who get caught up in them and are only really good for one use.

[0] https://www.google.com/maps/@48.2347588,-122.237414,3a,75y,3...

Spooky23• 4 years ago

They were common in the US in many areas but are seen as a liability as it’s easy to install them wrong.

doodlebugging• 4 years ago

The wire rope barriers have been installed all over Texas interstate highways which, in the past had no barriers to prevent traffic from crossing medians into oncoming traffic. A lot of bad accidents happened when vehicles crossed a grass median and slammed head-on into oncoming traffic. Years ago in an ice storm I almost became a statistic when a vehicle hit some black ice and the driver lost control, launching their vehicle across the median towards our vehicle.

They had installed miles of these wire rope barriers in the last 10 years and I have seen them being installed up in Oklahoma too.

Of course, once there is an accident the wire rope may have been strained past its rated capacity so it needs to be replaced. You can buy spools of the wire rope [0] from recycled materials handlers. Along the interstates near my place you will see skid marks into the cable barriers every time the highways get wet. If the weather was really bad you could find a dozen new collision spots in a 20 mile stretch. It keeps the repair crews busy. People drive too fast out here nowadays.

The pdf document posted is a great read. I see several barrier designs there that I have never seen in use anywhere and all the familiar ones too.

The most common barrier for many years in Texas has been the W-beam SGR04B type or similarly, the thrie-beam rail SGR09B but they tend to use treated timber posts for mounts. The newer installations have impact-absorbing lead-ins to help prevent fatalities.

A couple years ago I was driving home along a two-lane US highway (not an interstate) where the W-beams were used at every creek or river crossing. As I rounded a long curve in the highway headed downhill towards a creek crossing about 1000' away (305 m) I saw skid marks leading to the edge of the highway where the guard rails should've been. The skid marks were obviously made by an 18-wheeler (semi) truck-trailer. The guard rail was completely wiped out and as I passed the creek I saw where it came to rest. The entire length of rail was curled and twisted with one end up more than 30' (9.1 m) in a tree beside the creek more than 30' (9.1 m) off of the highway and the other end curled down near to the ground. It had been launched up into the tree by the force of the collision.

[0] https://www.repurposedmaterialsinc.com/median-galvanized-cab...

p1necone• 4 years ago

I know what I'm reading on my next road trip.

Arn_Thor• 4 years ago

That timber-faced guard rail looks fantastic! And I wonder if its "weak" outward appearance will cause people to drive more cautiously

defrost• 4 years ago

I started in engineering before moving into applied math backend numerical engineering .. I still appreciate the quiet understatement of phyical testing results such as:

To contain and redirect a 36,000-kg gasoline tanker after impacts at high angles and speeds, a 2290-mm (90-in) concrete barrier is required.

[ picture of hard impact big truck side humping and sliding into said barrier ]

rocketflumes• 4 years ago

saw a fascinating video on this topic awhile ago:

https://www.youtube.com/watch?v=w6CKltZfToY

ortusdux• 4 years ago

I've been wondering if the new Korean style rolling barriers would gain acceptance in the US and other countries.

https://interestingengineering.com/innovation/this-new-korea...

ultrarunner• 4 years ago

In the U.S. we're struggling to get them to understand that bike lanes and sidewalks can't just randomly end mid-block and still be useful. While the idea seems ostensibly solid, and cars very much need containment, we still have much more basic needs before we can start optimizing car infrastructure.

philwelch13• 4 years ago

No, we can start improving car infrastructure right away because, on the types of roads that have guardrails, cars are like 98% of the traffic or more. And the rare roads that have both guardrails and sidewalks should probably have the sidewalks on the far side of the guardrails, at which point improved guardrails also protect pedestrians.

Purely from a safety standpoint, outright prohibiting bicycle traffic on motorized roads would be a massive improvement at the expense of inconveniencing a small minority of people (while improving the convenience for everyone else). I'm kind of surprised more states haven't done it yet. Failing that, it's probably better to also use guardrails to physically separate the bike lanes from the motor lanes, which is yet another use-case for improved guardrails.

kube-system• 4 years ago

Looks expensive.

Part of the problem is that the US has a lot of roads. So often, the comparison that is made is not “which guardrail is the best”, but, “which places can we budget to install a guardrail?”

This is why even though the safety of cable barriers is disputed, the overall number of lives saved by them is usually said to be quite positive, because we can afford to install more of them. Hitting a shitty cheap guardrail (or cable) is usually better than hitting a vehicle head-on or hitting a bridge support.

Also, those end caps on that guardrail are not considered a safe design and aren’t really used in the US anymore because they spear vehicles when hit directly on the end.

elihu• 4 years ago

There was a recent story about one person who would presumably approve of this design: https://news.ycombinator.com/item?id=33412702

hammock• 4 years ago

They ought to put those on the outside of Nascar tracks

dementis• 4 years ago

That would just encourage more drivers to do what Ross Chastain did and probably make the race more about which driver can within the physical abuse of hitting the barrier.

2-718-281-828• 4 years ago

you mean for this sort of stunt?

https://www.youtube.com/watch?v=K3yNc5EasW8

at_a_remove2• 4 years ago

So, that little slope probably saved my life once.

I was trucking up 44 at a fairly moderate pace (I'm not a big speeder) around a curve when there was suddenly a car in my lane, so I jerked the wheel to the right lane ... where there was another car, I twitch back to the other lane and begin, well, hydroplaning or whatever it is when you have just a touch of rain to bring up the oil from the road. Brakes were not effective and I was headed right for the highway divider at somewhere between forty to fifty miles per hour, at a forty-five degree angle. In this flimsy little car, that corner impact is going to hit me pretty hard.

That's when I looked at the little slope at the base of the highway dividers and reasoned that if I could get my car parallel to the divider, the impact would be taken on the left wheels and the left side of the suspension, areas designed to bear some weight from that particular direction already. I managed to get the car aligned by tweaking the wheel direction, hit, slid for about ten or fifteen feet. I was so nearly perfect to parallel that I only lost the rubber covering to about an inch of bumper. Ended up replacing the tires a few weeks later just out of an abundance of caution, but otherwise fine.

(It turned out that there was a big wreck up around the curve and various drivers had decided to just sort of stop where they were, hence my surprise obstacles)

wffurr2• 4 years ago

I am glad you came out of that OK.

> fairly moderate pace (I'm not a big speeder)

But you were speeding, right? On a wet roadway with what sounds like poor visibility.

at_a_remove2• 4 years ago

No. You should read what I wrote.

YZF• 4 years ago

You weren't hydroplaning. Hydroplaning is when there's so much water your tires can't funnel that water out and you're driving on the surface of the water. You "just" lost traction. And yes the first rains of the season that bring up all the c*ap from the road are notorious for being slippery.

In situations like that you can try to regain traction by making sure the wheels are pointing at the same direction you are traveling, not being on the brakes, etc. Practice on snow or ice in a safe environment. I'm not that great at this myself but I have recovered traction in a handful of real life snow/ice scenarios... Go-karting can also develop some skill/feel for this. You can also take lessons...

Swizec• 4 years ago

You can also take lessons...

In my part of Europe (Slovenia) they now make you take a “safety driving” course within 2 years of getting your license. Skid plates, hydroplaning, all the fun stuff.

My sister got to do it. I missed the fun by a few years and instead practiced with lots of late night drifting fun on fresh snow (don’t tell mom :P)

atoav3• 4 years ago

Hydroplaning below 80 km/h ~49 mp/h is rare and the risk of the wheels loosing contact to the ground increases with speed. So not sure if this was really hydroplaning.

As a tip for others: If you ever encounter hydroplaning make sure not to keep your steering wheel straight (or at least: know why you are doing what you are doing) and step off the gas pedal.

In hydroplaning your wheels don't have contact with the road surface, so turning the wheel won't do shit. But as you loose momentum your wheels will regain contact appruptly again at some point. At that point it really matters how your front wheels are oriented when you do so.

If your front wheels point hard left and there is a dry part of the street you will be yerked directly into oncoming traffic for example.

tux2bsd2• 4 years ago

make sure not to keep your steering wheel straight

remove the "not".

(or at least: know why you are doing what you are doing)

Remove that too, it's unnecessary.

leetrout• 4 years ago

Ah! Always wondered why they called it a Jersey Barrier but had never looked it up.

kazinator• 4 years ago

The concrete barrier industry moves at a fast pace (so to speak).

I wonder how much of this stuff from 2000 is still relevant?

Back then moor anchor law was still in full swing, for one thing.

arcanemachiner• 4 years ago

What is "moor anchor law"?

w10-1• 4 years ago

These have been lifesavers. Highway 101 in South San Jose used to be called "Blood Alley" for lack of effective separators. The biggest reduction in traffic fatalities historically accompanied their adoption.

However the US improvement is 3-5X less than other similar countries. For details on that and links to some data sources, see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4103211/

Mistletoe• 4 years ago

I love reading this and seeing just how much science, math, and thought has gone into these. Most people driving by just have dunning-kruger and imagine anyone could throw some concrete barriers up and design them. The deeper I go into most things it seems I always find this to be true.

geocrasher• 4 years ago

I owe my life to these barriers.

In 1999 I was driving a '68 Plymouth Barracuda southbound on US395 in Reno, NV USA, doing 65-70mph in the fast lane (the lane closest to the middle barriers).

Being an older car, the 'Cuda had a tendency to drift to the left, toward the barriers. I corrected to the right, as I always did. Nothing happened. The joint connecting the steering column to the steering box, held together by a flimsy piece of sheet metal, had come apart.

I was now a passenger, and didn't dare not slam on the brakes, lest the all drum brakes send me in some unknown direction as they often did. If you're getting the idea this car needed some TLC, you'd be right.

With only a second or two to think about what to do, I simply let off the accelerator. The car started slowing slightly, but by the time the car drifted gently into the barrier, I was still travelling at at least 60mph.

My imagination saw me bouncing off the barrier, back into the fairly steady Reno afternoon traffic, where I'd be bounce like a pinball between other cars, eventually going sideways, flipping, and probably not surviving. I hoped nobody else got seriously hurt.

But that wasn't what happened.

The Cuda's front left tire caught the bottom of the barrier- the steepest angle the barrier has- and the front tires immediately slammed hard to the left. Now, both my front tires were at full lock left at 60mph. I expected to flip over.

Once again, that wasn't what happened.

Instead of flipping, the front left corner of the car became airborne for only a moment. Without traction, the front end just came back down, unable to continue its journey past about 40 degrees to the right. I'm guesstimating here, since at this point I was simply enduring the ride and out of my mind with fear. I didn't scream.

The cycle repeated itself, and each time the car lurched into the air, it lost speed. After several cycles, I realized that the car had stopped climbing the barrier and was the front tires were just skidding forward against the barrier and the pavement. It was only then that I thought it safe to press the brakes.

Finally, the car came to rest. After I stopped shaking internally, I realized the car's engine was still running. I turned it off. I was alive, and I realized in a very short time that I owed my life to the engineers who designed the Jersey barrier.

After reading this article, my appreciation soars even higher. All of the things that happened to me in my car weren't accidental: They were designed.

Thanks, Jersey barriers. I owe you one.

----

As an aside to that story, I was about to horse-trade that car (straight across, no money changing hands) for a 1969 Land Cruiser FJ55 wagon just that week. I was sure that the trade would be a bust, but when I looked out the window, I saw that the only body damage was a bent fender lip! The barrier's design really shined even greater in that moment.

$100 to a not very friendly tow truck driver got me and the car home, and the very next week I was driving a 1969 FJ55 wagon. That vehicle was actually less safe, but way, way, more fun. And the new owner? He was doing a ground up resto anyway, and didn't care about the bent wheel, ruined tire, and broken ball joint. It was all being replaced anyway.

xrayarx• 4 years ago

From the article:

The basic principles of concrete barriers are not generally known or understood. Concrete barriers appear to be simple and uncomplicated, but in reality, they are sophisticated safety devices.

mooneater• 4 years ago

I'm glad they are thinking through the details on barrier design.

Lets not forget that is only necessary because the automotive industry is barbaric to begin with. Let's recall why trains dont require advanced crash barrier design like this.

vwcx• 4 years ago

Your opinion on the barbarism of the auto industry will be considered heresy by many, but I applaud your ability to think outside the century of precedent that makes us feel that there are no options beyond what Henry Ford pushed on us.

jmkd• 4 years ago

There are a group of skateboarders dedicated to only (mostly) riding Jersey barriers: https://www.instagram.com/barrierkult/?hl=en

Basics of Concrete Barriers (2000)

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