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Can a single car break a traffic jam?

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Re: Can a single car break a traffic jam?

#21

Post by jerf »

revscat wrote: post #3

This is almost a perfect metaphor for the failings of capitalism, or at they very least the notion that the singular pursuit of selfish greed can lead to ideal outcomes. The selfish need for individual drivers to go as fast as they can leads to a collective failure, here in the form of a traffic jam.

You don't need "selfishness" to create traffic jams. You need only "latency in response"; if you response less than instantaneously to the car in front of you slowing down, and you response less than instantaneously to the car in front of you speeding up (especially if you accelerate even a bit conservatively, let alone late), you very quickly get amplifying waves.

Your post, if we're going to trade snarky political barbs, is a great example of how some people think that some magical form of "regulation" can regulate basic control theory right out of existence. Thinking that any form of regulation could somehow fix this is exactly the same as thinking that they could "fix" gravity. The physics is actually pretty simple at the core, even if the details are complicated. Anywhere you get negative feedback of a certain very, very popular and easy-to-hit form, you get waves. Can't be stopped.

Re: Can a single car break a traffic jam?

#22

Post by stevebmark »

Traffic jams exist because humans drive cars, and humans are not designed to process data at 120 kilometers per hour.

This is a major repost but still misses the main problem. When you look at a car in front of you, you perceive it as a stationary wall, not a moving wall. When you slow down, you're trying to avoid hitting where the car in front of you is when you press on the brake pedal. You're not smart enough to realize that you should be slowing down to avoid hitting where the car will be when that car stops.

You do this, and you should not be driving cars. Leaving space in front of you is an inefficient solution to this problem, now you're overcompensating even more for the problem.

You can try watching one car ahead of the one in front of you to predict when the car in front of you will slow down and need to stop. Your passengers will freak out, constantly thinking you're going to hit the car directly in front of you, because they perceive the car in front of you as a stationary wall. In reality, you're driving more efficiently.

The day when us unevolved meat sacks stop controlling two ton metal bullets can't come soon enough.

Re: Can a single car break a traffic jam?

#23

Post by GigabyteCoin »

logn wrote: post #15

I often try the technique of leaving lots of space and going at a slower, steady pace. One problem is that everyone re-routes around you, and you induce road rage and traffic weaving. The other problem is that unless it's a straight stretch of road, you have no idea what speed is slow enough.

Truckers (professional drivers) do this all the time.

If ever there is a traffic jam on the highway, you will see the big rigs consistently leaving hundreds of feet of space in front of them.

They also seem to concentrate in the center lanes of the highway for reasons I haven't figured out yet.

Re: Can a single car break a traffic jam?

#24

Post by j_s »

SwellJoe wrote: post #20
cft wrote: post #16

Earlier quoted context omitted.

AI will eliminate truck night stops, allowing them to be driven 24/7. Hopefully more trucks will be moving at night. That should reduce the jams.

Not only that, AI will eliminate huge amounts of wasted road even during peak times and with traffic that can't be scheduled for off hours (like people going to work/school). A networked self-driving car can know where the traffic is and route around it. It can provide tools to everyone (from city planners to individuals) to maximize the availability of resources and minimize the time wasted on waiting. Red lights ca…

Yes, all (but one?) lane going in the "to/from work" direction based on traffic needs will make a huge difference!

Re: Can a single car break a traffic jam?

#25

Post by daveguy »

noonshine wrote: post #12

I have adaptive cruise control in my Subaru Legacy and I have often wondered what will happen when more people have ACC. Or even if I were following another car exactly like mine - would the lag time grow exponentially with more intense stop/go or would it even out? Or does it depend on how well the car implements it?

I used ACC on my mom's hybrid Accord recently and it was an aweful experience. It was like regular cruise control, but broken. Lagging start, unnecessary distances, slow responses. That and the out of lane beep whenever I passed a car (staying in the same lane but getting to the edge of the lane for increased margin of error) was really annoying. If this is the future of assisted driving, just give me fully automated driving.

Re: Can a single car break a traffic jam?

#26

Post by paulmd »

cft wrote: post #16
cortesoft wrote: post #14

This sort of traffic jam dissipation is only applicable to phantom traffic jams. Here in Los Angeles, traffic jams are caused by too many cars being on the road. At some point, every available square foot of roadway is filled with a car. AI can help limit the amount of extra space taken up by air, but that will only moderately increase the number of cars that it will take before traffic hits. That number of cars will…

AI will eliminate truck night stops, allowing them to be driven 24/7. Hopefully more trucks will be moving at night. That should reduce the jams.

Increasing the efficiency of a process also tends to paradoxically increase its utilization (Jevon's Paradox). So it's entirely possible that automated trucking will actually increase total traffic volume.

Still though, even a few vehicles "eating traffic waves" can break up a traffic jam. I've heard the number put at 3-5% of traffic being self-driving would prevent phantom traffic jams.

So overall I would say that self-driving cars could help reduce phantom traffic jams, but they may actually increase real traffic jams caused by overcapacity.

Re: Can a single car break a traffic jam?

#27

Post by mhurron »

GigabyteCoin wrote: post #23
logn wrote: post #15

I often try the technique of leaving lots of space and going at a slower, steady pace. One problem is that everyone re-routes around you, and you induce road rage and traffic weaving. The other problem is that unless it's a straight stretch of road, you have no idea what speed is slow enough.

Truckers (professional drivers) do this all the time. If ever there is a traffic jam on the highway, you will see the big rigs consistently leaving hundreds of feet of space in front of them. They also seem to concentrate in the center lanes of the highway for reasons I haven't figured out yet.

> They also seem to concentrate in the center lanes of the highway for reasons I haven't figured out yet.

Most likely because if a lane is closed it will be an edge lane. Also, if you're on a 3 lane road and two lanes are closed, you only have to make one lane change to keep going.

Re: Can a single car break a traffic jam?

#28

Post by wnissen »

Johnny555 wrote: post #11
ianferrel wrote: post #2

The game Error Prone is cute, but it mostly shows that it's very difficult to keep going a constant speed when your only controls are a binary "Full Throttle" and "Idle".

Which is exactly how some people drive - an ex- used to make me car sick with the way she drove - rather than maintaing a constant speed, she'd speed up 'till she got too close to the car in front of her (dangerously close), then let off on the gas (or even tap the brakes) to slow down. Annoying and led to no end of arguments "Why are you always criticizing my driving!?".

With that style of driving, the minimum speed is also far more likely to drop to 0. And when one person is stopped, everyone behind them is stopped. Even for people who don't normally drive that way, add in a cell phone and that's exactly what starts to happen because they don't have enough remaining attention to avoid being "surprised" by a stopped car.

Re: Can a single car break a traffic jam?

#29

Post by DonaldFisk »

Traffic jams are often causes in the way the article suggests, and if you drive at the average speed, instead of the maximum legal or safe speed whenever you can, there's a good change the jam will have dissipated just before you reach it, and you'll get where you want to go just as fast. This means that the cars behind you (provided it stays behind you) also don't have to stop. Their drivers should thank you for saving their fuel rather than curse you for driving too slow.

To minimize fuel consumption, it's best to drive in the highest gear, at the lowest speed for that gear. Failing that, to drive at a constant speed in the highest gear for that speed. If you do have to slow down, ease off the accelerator and change down gears, rather than use the brake. This means thinking ahead. You can do this when approaching a red traffic light, so that it will be green by the time you reach it.

There are a few other tricks to save fuel, such as driving at the minimum safe distance behind a big rig, and using gravity on hills to slow down or speed up.

This is sometimes called hypermiling: https://en.wikipedia.org/wiki/Energy-efficient_driving

Re: Can a single car break a traffic jam?

#30

Post by bagacrap »

logn wrote: post #15

I often try the technique of leaving lots of space and going at a slower, steady pace. One problem is that everyone re-routes around you, and you induce road rage and traffic weaving. The other problem is that unless it's a straight stretch of road, you have no idea what speed is slow enough.

The other problem is that this isn't scalable. Imagine a traffic jam that stretches for miles. Now imagine that same jam where everyone has left an extra three car lengths in front of them. You're suddenly using a lot more road per car. Tailgating actually seems like the most efficient use of space to me, provided you tailgate effectively (don't yo-yo).
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