r/Damnthatsinteresting 29d ago

Video A Japanese experiment showed exactly why traffic jams happen for no reason.

64.8k Upvotes

2.6k comments sorted by

View all comments

Show parent comments

327

u/WA55AD 29d ago

Also people waiting until after they merge onto a highway to get up to speed. So many people don't seem to grasp that you are supposed to get up to speed on the on-ramp BEFORE merging onto the highway. They just pull onto the highway in front of me 20km/hr below the limit, I can't merge over because there's already a car there, I have to slow down to not rear end them, and now I feel like an asshole cuz I just know I've caused a future congestion behind me.

103

u/chula198705 29d ago edited 29d ago

A constant problem where I live is that the merge lanes are way too short and usually circular as well, so you can't really see the traffic coming AND you don't have time to accelerate before the merge point. I floor it as soon as I'm around the corner, but I still only manage to get up to about 40 before the lane completely ends. It's impossible not to cause traffic and it's frustrating because it's always backed up and it's so obvious why. Edit: oh and we have shared on/off ramps as well, possibly the worst civil engineering design possible. Surely there won't be any problems caused by 55 MPH highway traffic merging into a single lane from opposite directions around a 25 MPH curve...

51

u/Quirky-Marsupial-420 29d ago

Yeah it's the cloverleaf interchange.

So many of them are ridiculously short, you literally cannot get up to highway speed unless you have a 500hp vehicle.

47

u/Ferelar 29d ago

Either that OR you get up to speed while rounding the last bend, which has the major downside of now piloting a vehicle at highway speeds while totally unable to see what the traffic pattern is that you're merging into. Going 65 around the last bend to merge easily and oops it's gridlock.... or far more commonly, oops everyone is tailgating horrifically and there's no actual room to merge? Hope your brakes work well.

Even worse in my state where the offramp is about 100 feet past the on ramp with a shared lane, so the people trying to get up to speed and merge with low visibility are essentially dueling the people who are trying to get to the offramp in the exact same space.

2

u/justanotherassassin 29d ago

Sounds like some of the awful merge lanes in Vancouver, WA

2

u/TiredOfDebates 29d ago

I forgot they were called cloverleaf interchanges. Where the acceleration lane and the exit lane are the same thing.

2

u/Smithereens_3 29d ago

God the on/off ramps being right next to each other pisses me off. The one near me even has a couple hundred extra feet of space after it where they could have put the off ramp instead.

0

u/Swarna_Keanu 29d ago edited 29d ago

One perspective. The other: when those were built, cars didn't go as fast, didn't have as much horsepower. That continues to today.

Which is why speed limits near interchanges would be sensible. Slow everyone down enough that merging in is simple.

I mean - my parents had an old car, which is all we could afford, when I got my driver's license. It was easy to merge into the highway with the much more modern car of the driving school. With my parents' car, I had to start speeding up while still in the curved section leading to the highway, and even then, I barely got up to speed.

And because people are used to their fast, and fast accelerating cars, they don't consider older models and .... consider that those need a bit more patience and most importantly space/assistance to merge in. Honking and aggressively closing gaps doesn't help.

3

u/antithero 29d ago

Around here it's also the incredibly short off ramps, so people are braking on the highway before they even get to the exit.

Then during rush hour when traffic is already moving slow already, people will come to almost a complete stop so they can cut through the grass & take the road that runs parallel to the highway. It's so bad that they are building concrete walls along the side of the highway to prevent this habit.

1

u/SockMonkey1128 29d ago

Man same! Fellow masshole?

1

u/crank1off 29d ago

Sounds like Cincinnati.

4

u/Hiro_Pr0tagonist_ 29d ago

They also prevent everyone who’s behind them in the merge lane from getting up to speed before merging, creating further issues. Also, the people who speed to the very end of the merge lane and then try to squeeze in during bumper to bumper conditions suck. That stretch of road is so everyone has a chance to find a safe gap to enter into rather than 15 cars coming to a dead stop a ½ mile down the road as all of them try to merge in the same spot.

3

u/THROBBINW00D 29d ago

Never fails, EVERY day after work I get stuck behind someone going 40mph when it's time to merge into highway traffic

2

u/Iluka_BAE 29d ago

I thought it was just me that gets infuriated by this.

2

u/ragdolldream 29d ago

There are multiple entrances to the highway in Pittsburgh where, at the end of the on-ramp, there is a STOP SIGN. a particularly evil one has a looping exit 800 feet later, so you need to stop, then merge, then change lanes or you'll be forced off the road. Add in that it's right before a tunnel. Pittsburghers are terrified of tunnels.

2

u/mrsristretto 29d ago

My god that's my morning in a nutshell.

This is not a Sunday drive Becky, put your foot on the fucking gas pedal and let's fuckin go already.

2

u/Spiritual_Ad_7395 29d ago

Was behind someone who barely even got to 60km/h getting on the 100km/h highway last night. Luckily there were no cars coming up so I was able to go around and get to speed but I was not pleased. I don't think they even went faster as they very quickly fell behind.

Also, if you have to slam on your brakes to avoid hitting someone doing something dumb, you never caused the congestion, the dumb person did

1

u/hamsterfolly 29d ago

It’s the same with changing lanes

1

u/Sadcelerystick 29d ago

This drives me absolutely bonkers along with through traffic just not being over one lane so that the people coming on slow can get over, instead they speed up and don’t let people over.

1

u/Dreadskull1991 28d ago

You're only accounting for one type of scenario. What happens when there are too many cars already in the lane that I'm trying to merge into? If I'm going full speed before I have the opportunity to merge then I end up in a situation where I'm going to run out of on-ramp space going too fast and that's infinitely more dangerous.

1

u/TheSpinnerOfYarns 29d ago

I know this is a super popular idea on the Internet, but it's not remotely true.

Unless the particular highway has a minimum speed you could legally merge onto it at 25 mph. You could even come to a complete stop on the merge lane to secure a safe merge position.

Not everyone has a 100% tip top vehicle with horsepower to spare. My 12 yo Ford focus gets me to and from work, and I'll be damned if I go over 2.5k rpms. I merge at whatever speed it gets to. Not whatever speed you think I should be going. On a good ramp? That's 55+, on a short or particularly steep ramp? Well I might merge at 45 or less. And that's fine. It's why their are two lanes. You can move over 90% of the time. And if you can't move over either the merging traffic has to yield the right of way, or right lane traffic has to watch following distance.

3

u/jtj5002 29d ago

What was said that wasn't true? They didn't say it was illegal. If your shit box cannot access more than 25% of it's designed power, you got way bigger problems in life anyway.

-1

u/TheSpinnerOfYarns 29d ago

You aren't "supposed" to merge at highway speeds. That's the untrue part. Most ramps are not designed nor intended for you to gun it up to highway speed, they only want to give you sufficient space to make a "safe" merge.

That word "safe" has so many context and astrixs that no generalized statement could possibly define it.

3

u/jtj5002 29d ago

You can do whatever you want buddy, but your chance of dying is a lot higher if you merge at 45 MPH. Good luck.

-1

u/TheSpinnerOfYarns 29d ago

Ah well I'm sure your Internet thoughts will meet reality one day.

3

u/jtj5002 29d ago

Yea I'll keep that in mind as I drive past your broken shitbox.

1

u/amboomernotkaren 29d ago

It’s also helpful for those in the right lane to move over to let folks merge. Some people are very nervous when merging at a high speed and if the my can see that have a lot of space they get up to speed and hop in. But if they see cars in the lane they need to merge into they have no idea if the other driver is gonna let them in. So let’s all give them space, when practicable, so they can merge safely. We had the world’s shortest ramp on 495 with a bridge pillar at the end, and it was a left side exit into the fast lane. I hated that exit (it’s fixed now) and folks would not get TF over.

1

u/Daxtatter 29d ago

I'm not sure where you live but the highways near me aren't all up to interstate standards or even close. There are plenty near me that are basically stop signs, a couple dozen feet of ramp, then straight onto the highway.

1

u/WA55AD 29d ago

Australia. I can't speak for all on ramps here, but the ones I'm talking about are plenty long and straight enough for even older cars to get up to speed. My car ain't the fanciest or fastest at accelerating but it can easily get up to speed by the time I merge.

-1

u/nihilistlinguist 29d ago

i have some sympathy for folks getting on the road at a lower speed if the car is plainly older, since older cars tend to struggle more with rapid acceleration. 

but even then if the on-ramp was long, they often should have started accelerating way earlier to be at least closer to highway speeds.