What are "phantom traffic jams" and how can technology get rid of them?

Originally published at: https://boingboing.net/2020/05/28/what-are-phantom-traffic-jam.html


1 in 20 drivers being a sensible human being and not joining the stop-start/ooooh-there’s-a-space-imma-cut-in-right-here would solve the issue just as easily I suspect…

In the words of the Fresh Prince: “Yo back up now and give a brother room!”.


Put twenty cars in a big circle, equally spaced, start them all moving simultaneously, and challenge them to just keep the car in motion.

ETA: Sorry, I meant to reply to the topic rather than specifically to Squidgy


Given the potential for self-driving cars to also cause highway crashes and therefore traffic jams, there is possibly a break even point between causing and preventing traffic jams.

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Whenever this topic comes up I’m reminded of the original article I read about it. In the years since I’ve tried this technique and I feel like it works, or at least makes my drive less stressful. It takes discipline though and it’s still too easy to slip back into the old mode of late-braking and racing to fill gaps, even though I know I’m making things worse.


Did they miss lane changes as a trigger? :thinking:

Yeah, except that I see truckers and non-aggressive “regular commuters” fixing these situations all the time on our larger roads. So 1 in 20 cars being “well behaved” does the trick too, I imagine.

They (I) just hang back and try to keep a steady speed just below the average of what we can make out ahead, which if the trucker is on their CB, is a ways ahead. If anyone ever gave me grief for doing that I’m sure I missed it. Usually drivers behind me just take the same steady pace and we all get where we’re going more quickly, more cheaply and with less wear and tear on the brakes in the end anyhow.

So rather than instrumenting the crap out of everything, why not just take data from existing traffic cams and either reduce the speed limit or send in a pace car. (ed: here we go: a 1956 Popular Mechanics article on the pace car approach and a simulation study from 2010)

At least the video didn’t suggest a crowd-sourced, blockchain solution based on smart contracts for road usage… :roll_eyes:


The truest statement in this video…

"Drivers make traffic worse."


Since being made aware of this technique I’ve noticed that this is how truckers drive too. Whether this is intentional or by necessity (trucks need more time to stop and start) I don’t know, but I’ve gained a new respect for them since then.


I’ve gained a new respect for them since then.

The drivers on the big rigs? Almost always an asset on the roads. Pro drivers and smart operators.

Dump trucks, at least around here, often clearly under-trained, under stress and behaving badly.

Just south of the Toronto Airport on the 401 there’s the approach to the Dixie Rd exit, which has a lot of truck traffic. I always get a polite “thank you” flash when I wave in the big trucks trying to cross to the exit.


Interestingly, models have shown had just one self-driving vehicle for every 20 human-driven vehicles can dampen a stop-and-go phantom traffic jam wave.

I am reminded of this passage from John Brunner’s The Jagged Orbit (1969):

[Tactics by which rebels seize power] go way way back to the industrial unrests of the nineteenth century, at least, and probably a good deal further. What [fictional rebel Morton Lenigo] did in Britain followed exactly the same pattern. He exploited the long-standing truth that if you can get five percent of the population behind any movement, whether it’s pro or anti, you can bring down governments.

Permalink: “Reducing phantom traffic jams is like seizing power in a rebellion

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When I had to commute in SF bay area traffic (1998-2007), I would try to keep my speed to the average of the typical race/stop swings. It would only last a few minutes before everything ground to a complete halt, but I like to think I helped a little.

EDIT: Just watched the video. Yeah, like that.

It does make me wonder about human drivers, and whether it could be improved with better driver training. I recall hearing that driver training in (waving hands non-specifically) Europe is much more stringent than in the U.S. – Comparisons would be interesting, I think.


self-driving cars that are aware of the traffic conditions ahead

Maybe first we should make sure self driving cars are reliably aware of what’s right in front of them?


Or, given how coronavirus and lockdowns have shown us that not everyone needs to commute every day, how about we:

  1. keep decreased car traffic

  2. decouple access to gainful employment from car ownership

  3. turn excess paved area into parks and spaces for human beings to inhabit


Alternately, having dynamically set speed limits works too.

Or I should say, work in Europe. Americans would never tolerate them.


Driving this way also burns less fuel. I am always amused by drivers who accelerate in order to get to a red light first.


In my experience you can help a bit but you can’t completely counter the effects of the guy not paying attention when changing lanes, and randomly adjusting speed from 10-under to 20-over in the left lane only to dive across 4 lanes of traffic at the last second to try to shove his way into the exit ramp where the traffic is completely stopped.

It’s really hard to clear up a standing wave jam because the effective capacity is dropped below the current load on the road. Even if only 1:1000 drivers is an asshole there are tens or hundreds of thousands of drivers that are going to take that road each morning or evening and it only takes one to fuck it up for the duration of rush hour. Ironically, about the only way for them to clear is for someone else to make an error up the road from them so the total load drops enough for the jam to clear.


The thing that drives me crazy is drivers who ride their brakes all the way down a hill to maintain exactly the speed limit, then stomp the gas and do +10 or +15 up the next hill. Of course this means the big lumbering truck behind them ends up doing -10 or -15 up the same hill, all in the left lane of course because lane discipline is unheard of.

I’ve heard people do that to avoid police speed traps at the bottoms of hills, but it seems to me that the police can hide better right behind the crest of the next hill.

…the bumpers of drivers following the speed limit. Some folks speed everywhere - school zones, residential areas, campuses full of crosswalks, or side streets with intersections as far as the eye can see. Nine times out of ten, after watching them weaving in and out of lanes, passing in no-passing zones, and cutting off all types of vehicles (including semi trucks, which can’t stop on a dime) you meet them again at the next traffic light. :roll_eyes:


It’s kind of funny that they go straight to self-driving cars as the solution. Some other things that might help, off the top of my head, without going full Skynet:

  • Smart Speedometers. If your AI thingy detects that you could avoid a bunch of stop and go frustration by slowing down slightly now, there’s an audible chime, and an LED around the perimeter of the speedometer lights up. Take your foot off the gas and slow down until the speedometer needle points at the light, and you should be able to coast straight through without braking.

  • Smart Cruise Control. Like regular cruise control, but it’s got the freedom to lower the speed by up to 10% if the AI thingy detects that doing so would avoid running into the back of a traffic jam. If the needed adjustment exceeds 10% of the speed you set, the smart speedometer feature kicks in. Human drivers would still need to do nearly as much active driving as with a regular cruise control.