I love re-deriving the train when people talk about autonomous cars/trucking and how they can already do the highway part easily

And instead of each one having a small engine, we could combine it all into a big one more efficient than separate ones would be!

Some sort of linked car-train lane that your car could use self-driving software to enter and leave would be an interesting concept. Like HOV but everyone is linked at the same speed.

And hey, since the cars are attached and all need to go to the same place

And voila, you just invented road networks again

my man have you ever been in, like, another country?

It’s a little of column a and a little of column b. When I’m driving and some absolute piece of garbage is riding directly next to the car to their right, I equate them to a blood clot, which is funny, because they also make me feel like having an aneurysm. I also don’t forgive the driver on the right, because they are more than capable of allowing a space for other drivers to pass.

The absolute lack of awareness on the road is startling. I swear to God, people are looking through straws and their neck doesn’t move.

Building extra lanes, though, does not solve the problem.

Indeed - play with them here!

traffic-simulation.de

I agree, I think mythbusters did a small scale test in a circle.

It’s like a pressure wave! The boat is gone, but the wake is still causing you problems.

Tried it. Now I’m stopped bumper to bumper with the guy who cut me off to cram his truck into the buffer I left. What’s the next step?

If I leave any kind of gap between me and the car in front, it is an inevitability that some jackass will swoop in to cut me off. Happened 7 or 8 times just yesterday. Texas drivers are a menace

I learned this technique – we called it “cutting off the head of the snake”.

Traffic moves like water, and becoming fluid and just rolling sometimes can kill traffic completely, I was on a stretch of bright red (5-10 mph) that began moving at 55 MPH after patiently rolling – there was no actual reason for the traffic jam.

Driving stick, I would do this all the time. In fact, I’d do it in the left lane, which I would never do, but for the fact all of the lanes are just constant stop and go. I’d leave massive buffers, 20-30 cars, and just cruise 5-10mph, and never stop. I just don’t understand why anyone wants to use their brakes at all, I hate using my brakes. I’d rather just coast in perpetuity than feel inertia in any direction.

From above the whole thing looks like an accordion. Drivers who tailgate tend to overreact when they see brake lights 50 feet in front of them, compound this by the guy tailgating them and so on. Leave a buffer to absorb this and it smooths out

All it takes is one guy behind you checking his phone, getting distracted so he gets cut up to create another stop start system about 5 cars back.

You’re vision of the traffic jam is a fragment of the entire pie.

people who insist on going full speed and then SLAMMING their brakes drive me to drink, and this applies to literally all modes of transport.

If you’re walking through a grocery store and are about to round a corner, fucking slow down so you have time to see anyone else coming your way, then you can speed up again when you know the coast is clear.

If you’re driving a car and coming up to a red light, or even worse a pedestrian on a crossing, FUCKING SLOW DOWN and just coast slowly, it’s not worth the off chance that you get to blast through at full speed, not for you or anyone else.

When I do this, I hear horns behind me, telling me to stick it into the car in the front, which is clearly stopped on a red light counting down from 20s.

At least 1/10 of them are idiots.

also, very respectfully to my mom and grandpa (RIP) old people have to stop driving. My mom is 65 and in pretty good shape so she refuses to stoo driving. She only have 2 road modes: Maniac or Tourtle. She’ll alone create a standstill in a highway OR she’ll almosr kill herself and everyone else on the road. No midle ground

Yeah but I’m trying to GO smoothly and courteously. Somewhere up ahead someone (or many someones) is stopping or merging badly or doing something else stupid to create these phantom traffic jams.

There’s more to it than that - there’s a lot of research involved. Other factors involve:

• Nobody does anything at the exact same time.
• What’s a turn signal
• I’m the main character!
• Hold on my phone’s ringing
• I’m getting in front of you if it kills you!
• Shit I’m gonna be 1 minute late for work!
• Fuck you in particular!
• One snowflake fell, time to panic!
• ALL the snowflakes fell but who cares I’ve got 4wd!
• Fuck this traffic, I’m taking the shoulder!
• CRASH
• Oh shit a cop everybody slow down.
• And more!

Chief offender is the cascade effect. Basically, there is a minimum convenient distance one can follow another at a given speed in given conditions. If thee guy in front of them does anything but keep going, they should be able to deal with it without slamming on the brakes.

But if people follow more closely than that, especially because the traffic volume increases, then when car A slams on their breaks, so do cars B, C, D, E, etc. then because everyone’s reaction speeds are marginally different, by the time you get to car F, everyone’s come to a hard stop, while car A goes on, oblivious that they created a traffic jam that may or may not have been inevitable.

I’ve had the same fascination!

A video I really enjoyed was a simplified experiment where they had some cars drive around in a closed loop - a single lane circle.

Traffic jams still inevitably somehow popped up, suggesting that we’re simply bad drivers haha. Higher level autonomous cars cannot come fast enough.

It becomes much harder to zipper merge, when there is a red light ~500m ahead and said 500m is almost full.

I also hate it when I am waiting at a red light and someone nearby suggests me to just skip the light, because I won’t get a fine (bicycle). I feel like people taking a test for the license (and renewing their license) should be reminded that the reason traffic laws exist is to prevent traffic jams and accidents.

deleted by creator

While things like merging movements and so on is part of the story, it’s not the whole story.

You see, by saying “traffic jams are caused by merging mistakes and so on” it kinda implies that if everyone drove perfectly a highway lane could carry infinitely many cars. In actually a highway lane has a finite capacity determined by the length of the vehicles traveling on it, the length of the gap between them (indirectly determined by how fast they can start and stop), and the speed they’re moving.

There are finite limits for gap widths and speed determined by physics and geometry. As the system approaches these limits it becomes less and less able to deal with small disruptions. In other words, as more cars move on a freeway a traffic jam becomes more and more likely. The small disruption which is perceived as the cause was really just the nucleation point for a phase change that the system was already poised to transition through. If it wasn’t that event then something else would trigger it.

It is interesting to note that once a highway has transitioned from smooth flow to traffic jam its capacity is massively reduced, which you can see in the graphs in the above link. Another interesting thing to note is that the speed vs volume graph, if you flip it upside down, resembles a cost / demand curve from economics, where volume is the demand and time spent commuting (the inverse of speed) is cost. If you do this you see something quite odd, which is that the curve curls up around itself and goes backwards.

This is less like a normal economic situation (the more people use a resource the more they have to pay, the less people use it the less they have to pay) and more like a massively multiplayer version of the prisoner’s dilemma. For awhile the cost increases only slightly with growing demand, until a certain threshold where each additional actor making a transaction has a chance to massively increase the cost for everyone, even if consumption is reduced. Actors can choose to voluntarily pay a higher time cost (wait before getting on the freeway) to avoid this, but again, it’s the prisoners dilemma. People can just go, trigger a traffic jam anyway, and you’ll still have to sit through it + all the time you waited trying to prevent it.

Self driving cars are often described as a way to eliminate traffic jams, but they don’t change this fundamental property of how roadways work. It’s true that capacity could potentially be increased somewhat by decreasing the gap between cars, since machines have faster reflexes than humans (though I’m skeptical of how much the gap can really be decreased; is every car going to weigh the same at all times? Is every car going to have tires and brakes in identical conditions? Is the condition of the asphalt going to be identical at all times and across every part of the roadway? All of these things imply a great deal of variability in stopping distance, which implies a wide safety gap.), but the prisoner’s dilemma problem remains. The biggest thing that self driving cars could actually do to alleviate traffic jams would be to not enter a highway until traffic volumes were at a safe level. This can also be accomplished with a traffic volume sensor and a stop light on highway on-ramps.

Of course trains, on top of having a way higher capacity than a highway lane, don’t suffer from any of this prisoner’s dilemma stuff. If a train car is full and you have to wait for the next one that’s equivalent to being stopped at a highway on ramp. People can’t force their way into a train and make it run slower for everyone (well, unless they do something really crazy like stand in the door and stop the train from leaving).

Same I moved to a place that lets me take mostly side roads to get in to work and I’m loving it. It is about 10 minutes longer than the highway if everything is perfect but if you account delays caused by traffic its usually almost even or faster if there’s a bad accident or something.

Me, in an empty bus, standing with people who could just sit in the bus with me so the street would be empty

Quite a few cities in the Northeast are designed this way, because they were done so in the 1950’ swith the intent of highway traffic doing 40, maybe 45 MPH through town at maximum. To conserve expensive urban land, they have short ramps and merge areas that were appropriate for those speeds, not to mention the lower overall volume of traffic in those times. And now we’re stuck with it, because it’ll be a 200 year long court battle to eminent domain the 427 landowners who are all clinging to five square feet each in the patch you’d require for a longer ramp, all hoping for a fat payout to let go of it.

And nowadays, of course, everyone takes it as their god given right to do 90+ MPH on the freeway at all times, and get frothingly pissed off if they can’t for any reason whatsoever. So the ramps aren’t long enough anymore because no one is using the highway as designed.