How Nissan leveraged its driver assist to cut traffic jams

Cooperative cruising cuts congestion in Contra Costa during ProPilot pilot study.

See full article...

 

[noxylophone]

I-680 is a notoriously bad traffic corridor; good place to test.

But folks, leave a big gap ahead when driving in heavy traffic. Doesn’t take too many people doing that to start to break up the pressure waves that propagate through traffic jams, to everyone’s benefit.

 

[Hammer_Thyme]

This is very cool research

 

[peterford]

Instead of DSRC, the cars use their embedded LTE modems to communicate via Nissan's cloud.

What you have is better than a theoretical perfection you don't, but I can already hear the later comments about cloud dependency and latencies.

 

[CrystalCowboy]

... informing other cars about their speed and any hazards.

Legal ramifications of your car ratting you out.

 

[Derecho Imminent]

"The information from the probe car lets the following cars keep an appropriate distance from each other—between 30 and 60 seconds"

Thats gotta be a typo. No way that car in the picture is 30-60 seconds behind the car in front of him. I cant even imagine any scenario where that would be valid. Even 3-6 seconds is stretching it.
oops

 

[UnnDunn]

I was honestly wondering how long it would take for automakers to start experimenting with traffic mitigation systems like this.

Hopefully this can be made into an industry-wide standard, so that cars from all manufacturers can talk to each other.

 

[UnnDunn]

Is that 30-60 second gap for real? Seems like there isn’t any traffic at all if you can leave half a mile between vehicles. I’m suspecting a mistake somewhere. Even 6 seconds would be a big gap to find in heavy traffic, I expect.

Did they test this at 3am? It's not clear how else they were able to keep a 30-60 second following distance from the car in front of them on 680 - 3-6 seconds (or less) seems more typical. 30 seconds is half a mile @ 55mph.

FFS read the article or even just look at the diagrams! The test cars maintained a 30-60 second gap to each other, but regular traffic was mixed in between them.

 

[georges]

It seems clear that the "probe" car is way ahead of them and getting stuck in the waves of braking, hence the 30-60 seconds lead time. It would have to be way ahead of them to communicate and have them react in time.

The CCM cars are not directly behind the probe car... it is ahead "probing" traffic.

Ninja'd by UnnDunn and yeah... rtfa.

 

[atmartens]

The simple solutions to reducing traffic jams aren't technological, as it's already well understood that reduced speed limits help reduce congestion through several mechanisms, including reducing the stopping distance (and therefore the safe gap distances between cars), and also by reducing the probabilities of car collisions, which in turn reduces the chance of major backups behind crashes.

When there is a traffic jam, people also psychologically feel pressured to speed up as soon as a gap appears, otherwise someone else might switch lanes to "plug" the gap, and people don't want to feel like they are holding up the others behind them (plus some wishful thinking that the traffic jam has ended and they can again speed up to the limit). Unfortunately, this just contributes to the speed up & brake hard phenomenon discussed in this article.

Finally, slower speeds on highways better match slower speeds off of highways, which alleviates the on-ramp/off-ramp mismatch bottleneck. A great example is the speed limit reduction on Paris' boulevard peripherique (ring road). People actually reach their destinations faster with lower speeds!

 

[nuurdin]

It's sort of sad how much it surprises me to see non-malignant uses of technology. But yeah, this is cool. Neat (although not entirely surprising) that they see benefit at that low penetration rate -- I am really looking to seeing more on this.

 

[mghmgh]

"The information from the probe car lets the following cars keep an appropriate distance from each other—between 30 and 60 seconds"

Thats gotta be a typo. No way that car in the picture is 30-60 seconds behind the car in front of him. I cant even imagine any scenario where that would be valid. Even 3-6 seconds is stretching it.

My understanding is that this is the distance between the cars equiped with this system. There are other normal cars between them. So you have some kind of 'traffic regulator cars'every 30-60 seconds, and this helps keep all the traffic going at a better flow.

 

[UnnDunn]

The simple solutions to reducing traffic jams aren't technological, as it's already well understood that reduced speed limits help reduce congestion through several mechanisms, including reducing the stopping distance (and therefore the safe gap distances between cars), and also by reducing the probabilities of car collisions, which in turn reduces the chance of major backups behind crashes.

When there is a traffic jam, people also psychologically feel pressured to speed up as soon as a gap appears, otherwise someone else might switch lanes to "plug" the gap, and people don't want to feel like they are holding up the others behind them (plus some wishful thinking that the traffic jam has ended and they can again speed up to the limit). Unfortunately, this just contributes to the speed up & brake hard phenomenon discussed in this article.

Finally, slower speeds on highways better match slower speeds off of highways, which alleviates the on-ramp/off-ramp mismatch bottleneck. A great example is the speed limit reduction on Paris' boulevard peripherique (ring road). People actually reach their destinations faster with lower speeds!

I know there are places in Europe and Asia where they implement dynamic speed limits to mitigate traffic jams, but good luck implementing that in America; it'd never be successful. Drivers would ignore the dynamic speed limit, and police would not enforce it worth a damn.

 

[MiggityMikeB]

This is the future right here. Even having just a few cars in the mix talking to each other and making the pace would be beneficial.

 

[RockIslandLine]

I know there are places in Europe and Asia where they implement dynamic speed limits to mitigate traffic jams, but good luck implementing that in America; it'd never be successful. Drivers would ignore the dynamic speed limit, and police would not enforce it worth a damn.

Chattanooga does it.

 

[UnnDunn]

Which means that we just need to reduce the speed limits permanently. Speed limits used to max out at 55 mph in the US, and there's no reason why we can't do that again.

Yeah, I kinda figured that's the position you were going to take. Good luck with that idea.

 

[noxylophone]

Which means that we just need to reduce the speed limits permanently. Speed limits used to max out at 55 mph in the US, and there's no reason why we can't do that again.

lol no

 

[MiggityMikeB]

I know there are places in Europe and Asia where they implement dynamic speed limits to mitigate traffic jams, but good luck implementing that in America; it'd never be successful. Drivers would ignore the dynamic speed limit, and police would not enforce it worth a damn.

We have dynamic speed limits on 217 in Oregon. They're actually helpful, but you're right that some people ignore them. Just knowing there is slowing ahead and following the slower suggested Advisory speeds can help keep traffic moving, it cuts down on full on jams and tailgating idiots from running into each other as often. It's not really enforced by police, no need for enforcement because if someone ignores it they just get to the slowdown sooner. Similar to this article about cars communicating with each other about traffic, you don't need all the cars doing it just enough to help traffic.

https://www.itskrs.its.dot.gov/2016-b01079
https://transops.s3.amazonaws.com/uploaded_files/NOCoE RWM Peer Exchange - Oregon VSL.pdf

 

[Perrin42]

I think if we implemented the concept of "Keep Right Except While Passing" it would help as well. I often see the right lanes moving faster than the left lanes in California traffic, even with all the big rigs there, because so many people move to the far left lane and shut their brains off.

 

[noxylophone]

Chattanooga does it.

So does Seattle.

 

[director_mr]

Agree.
Most reckless drivers that speed, embraced Bush administration push for 65MPH from 55MPH and up (see Montana) for speeds as high as 75MPH. However the interstates were no designed for this, as the acceleration/deceleration lanes were engineered for 55MPH (with some no higher than 75MPH). So you need to punch it to merge, or slam on brakes faster to exit. And those ramp curves are designed to force you to slow down, else over you go (or into the guardrail if there is one).

Less than 30 mins ago, I was out at the crosswalk to grab some breakfast from local venue. I watched as a driver of a Jeep SUV, decide to pull out into the other crosswalk but block opposing traffic. There was a vehicle trying to park down that street, holding up a oneway street into the crosswalk. But the JeepSUV driver would not allow anyone to go, until she (I walked past, making a face as she rolled her window down to yell at the car trying to back in...and she would not yield to her!). Obviously a Karen in the JeepSUV... so I just SMH... well, Carma would have it that after the car parked, the "Karen in the JeepSUV" exhibited speed and skidded to stop as a garbage truck pulled out in front of her. The carma is strong with me!

Where does this idea that 55 mph is super safe and amazing and 65 mph or 75 mph being the absolute unsafe killers of all of our children come from? There is no reason properly engineered roads and vehicles, and drivers following traffic laws can't make a 75 mph highway safe. Conversely stupid roads and driving can make even 45 mph dangerous. I would rather we focused on making going 75mph safer.

Focusing on speed alone "SPEED KILLS!" is kind of silly. What kills is rapid changing of speed.

 

[Steve austin]

The dependence on LTE service and the Nissan cloud implies that this would be yet another subscription service. DSRC at least had the potential to avoid that. I fear that at some point some functionality will come along that will effectively make some sort of “connected” subscription mandatory.

 

[PoliteFun]

"The information from the probe car lets the following cars keep an appropriate distance from each other—between 30 and 60 seconds"

Thats gotta be a typo. No way that car in the picture is 30-60 seconds behind the car in front of him. I cant even imagine any scenario where that would be valid. Even 3-6 seconds is stretching it.

The picture shows that there are other (non-equipped) cars in this gap. This shows you don't need every car to have this system in order to benefit.

 

[Derecho Imminent]

My understanding is that this is the distance between the cars equiped with this system. There are other normal cars between them. So you have some kind of 'traffic regulator cars'every 30-60 seconds, and this helps keep all the traffic going at a better flow.

Oh ok I see. So a just a few cars slow down and that makes all the other cars slow down? IDK if that will work. It just seems like when people start talking about that guy that goes too slow its always either a rage post or complaints about how people keep jumping into the gap in front of him.

edit: ok, now I see. Its not about the distance but about the headsup that conditions are changing.

 

[Cthel]

Oh ok I see. So a just a few cars slow down and that makes all the other cars slow down? IDK if that will work. It just seems like when people start talking about that guy that goes too slow its always either a rage post or complaints about how people keep jumping into the gap in front of him.

It seems like an enhancement to the "watch the brake lights of the car 5 cars ahead of you" that you're meant to be doing in traffic (so you can start slowing down when you see that car slow, rather than slamming on the brakes when the car right in front of you hits the brakes), but not limited by line-of-sight thanks to the RF-based comms.

 

[TheShark]

Pro reading comprehension tip: if something in the article comes across as completely outlandish or unbelievable ("did they test at 3AM? How did they leave a half mile gap between cars!"), that's a clue that you misread the text and you should go back and read it again.

 

[FishInABarrel]

I know there are places in Europe and Asia where they implement dynamic speed limits to mitigate traffic jams, but good luck implementing that in America; it'd never be successful. Drivers would ignore the dynamic speed limit, and police would not enforce it worth a damn.

They had dynamic speed limits on I-270 in Saint Louis for a while, and you're absolutely correct. No one pays attention to the posted speed limit. Everyone is just driving at whatever speed they're comfortable with.

 

[SirOmega]

I was honestly wondering how long it would take for automakers to start experimenting with traffic mitigation systems like this.

Hopefully this can be made into an industry-wide standard, so that cars from all manufacturers can talk to each other.

There were plans many years ago to use the V2V Safety spectrum at 5.9GHz (75MHz) to do this stuff. Nothing has every really panned out, which is unfortunate given the results above. I think the difficulty would be securing the spectrum to prevent bad actors from maliciously broadcasting bad data into the system.

 

[some guy in San Diego]

I think if we implemented the concept of "Keep Right Except While Passing" it would help as well. I often see the right lanes moving faster than the left lanes in California traffic, even with all the big rigs there, because so many people move to the far left lane and shut their brains off.

The right lane moves faster sometimes (particularly in highways with lots of lanes which are very common in major urban areas in CA) because everyone gets out of the right lane as quickly as possible to avoid merging ... which means it's usually pretty clear, so people who like to drive way faster than the flow of traffic spend a lot of time in the right lane. I'm not saying people sitting in the leftmost lane isn't a problem (though not many people do it when there are >3 lanes per direction), but what you're seeing is basically just people who are trying to go as fast as possible driving where there's the least traffic.

 

[UnnDunn]

There were plans many years ago to use the V2V Safety spectrum at 5.9GHz (75MHz) to do this stuff. Nothing has every really panned out, which is unfortunate given the results above. I think the difficulty would be securing the spectrum to prevent bad actors from maliciously broadcasting bad data into the system.

Commonplace encryption technologies would secure the system against bad actors like that. Data being broadcast would be digitally signed by the automaker, and if one is found to be broadcasting problematic data, the other automakers would simply blacklist that signature and ignore data signed with it.

 

[trailerpark1976]

This is really cool tech. Unfortunately I think the real thing that will hold this back is finding a way to monetize it for the car company that installs it on their vehicles. The line MUST go up!

 

[real mikeb_60]

I think if we implemented the concept of "Keep Right Except While Passing" it would help as well. I often see the right lanes moving faster than the left lanes in California traffic, even with all the big rigs there, because so many people move to the far left lane and shut their brains off.

I've long observed that. Another factor that makes life uncoomfortable (at best) in the left couple of lanes is how people react to the smallest gap opening in front of them: they typically floor it to close the gap, then stand on the brakes as the ones in front slow down again. A study done many years ago with lidar chase cars in LA traffic observed frequent accelerations of near-drag-race proportions, sometimes (briefly) up to 2-3x the surrounding traffic, then full-effort braking, in the left lanes of a stop n go freeway. The right lanes typically ran at about the average speed of the traffic, with far fewer hard accel/braking events.

I used to take advantage of that when driving a stick shift. Tootling along at 15-20 mph in the #3 (from the left) lane (of 4 or 5), leaving a car length or 2 in front of me, allowed speeding up or down a little but seldom braking hard, usually in 2nd or 3rd gear without having to shift often. Far more comfortable than having to constantly row the gears to accel hard in the left lane only to stop completely again (the inchworm effect). And, picking some easily identifiable car in the left lane, I would usually reach the end of the 10 miles or so of complete jam within a minute or so (and sometimes faster) than them. Perhaps the best "manual" way to do what Nissan is trying here would be to make everybody drive stick in traffic?

 

[evan_s]

We have dynamic speed limits on 217 in Oregon. They're actually helpful, but you're right that some people ignore them. Just knowing there is slowing ahead and following the slower suggested Advisory speeds can help keep traffic moving, it cuts down on full on jams and tailgating idiots from running into each other as often. It's not really enforced by police, no need for enforcement because if someone ignores it they just get to the slowdown sooner. Similar to this article about cars communicating with each other about traffic, you don't need all the cars doing it just enough to help traffic.

https://www.itskrs.its.dot.gov/2016-b01079
https://transops.s3.amazonaws.com/uploaded_files/NOCoE RWM Peer Exchange - Oregon VSL.pdf

I'm glad I no longer have a daily commute on 217 anymore. If I was going into the office regularly I'd be going over 217 but not on it.

Our 2019 Leaf SV+ does have the Pro Pilot that's mentioned in the article. It seems decent enough for a hands on driver assistance package. It's no Tesla FSD (or what ever they are calling it now) but it works reasonably well in my limited use. I assume there's basically 0 chance this would end up getting pushed out to existing vehicles since it doesn't have any OTA updates.

The idea seems simple enough and makes sense. Slowing the traffic flowing into an area of congestion gives it a chance to break up a bit or at least slows down the compounding that causes it to get worse.

 

[plarstic]

I know there are places in Europe and Asia where they implement dynamic speed limits to mitigate traffic jams, but good luck implementing that in America; it'd never be successful. Drivers would ignore the dynamic speed limit, and police would not enforce it worth a damn.

In the UK the dynamic speed limits on highways are usually enforced with nearby speed cameras that read your number plate (it's called ANPR) and issue an automatic fine when you're over the limit by a certain amount.

 

[DonColeman]

Bay Area driver here -- I try to do a bit of this by looking ahead as far as I can, and adjusting my speed also to those cars not just the car in front of me. It's gotten a lot harder over the decades as vehicles keeping getting bigger and bigger -- just can't see past them!

When I can see far enough ahead, I definitely can smooth things out -- less and smoother breaking, almost never coming to a full stop. I figure this reduces my fuel use and saves a bit of the breaks ... an EV would get even more benefit. I can also see in my rear view mirror that it even lasts for a couple cars behind, but it definitely fades.

Having more cars (and hopefully in front of me!) would be great.

 

[Derecho Imminent]

I think if we implemented the concept of "Keep Right Except While Passing" it would help as well. I often see the right lanes moving faster than the left lanes in California traffic, even with all the big rigs there, because so many people move to the far left lane and shut their brains off.

Roadways that are already nearing capacity would jam up. You can only fit half as many cars in 1 lane that you can in 2 lanes.