Adaptive cruise control could ease "phantom traffic jams" - or make them worse

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Some years ago, I remember reading that if just a few of us started driving cars with this new technology called "adaptive cruise control", traffic would flow faster and smoother (2008 article):

While traffic congestion in the reference scenario was completely eliminated when simulating a proportion of 25% ACC vehicles, travel times were already significantly reduced for much lower penetration rates. The efficiency of the proposed driving strategy even for low market penetrations is a promising result for a successful application in future driver assistance systems.

 
In one experiment, the team filled a lane of traffic with seven identical vehicles -- all running the same ACC system -- with a pace vehicle in front.

Once all vehicles achieved a cruising speed of 50 miles per hour, the pace vehicle quickly reduced its speed by 6 miles per hour.

In a domino effect, each of the following vehicles slowed down more and more dramatically so that, by the seventh car, its speed dropped below the minimum required for the ACC system to operate.

(From the article)


What is your experience? I feel like the ACC in my Accord is worse than my personal driving behavior. But I think the researchers are right: there has got to be a way to implement it that could smooth traffic. I don't think we're there yet, and we may even be making traffic worse.
 
I agree with @brages…my personal driving behavior is better and far smoother than my ACC in my two Toyotas.

It constantly brakes and accelerates far too far aggressively. Now this may not be entirely the fault of Toyota (the only brand of ACC I have used) because it follows the vehicle ahead. And here in the northeast 60% of the drivers have not earned and/or remotely comprehend the privilege and responsibility of operating a vehicle.

I have always gotten many many miles brakes. I would bet that continued use of ACC significantly lessens brake longevity and deceases MPG’s vs traditional cruise control.

We have become a highly foolish society; ACC is not going to create less traffic. Why you ask? Because fools can legally operate motor vehicles.
 
I abhor ACC because, when combined with drivers who don't follow good lane discipline etiquette, they just jam up the passing lane. It most certainly actually REDUCES average driving speeds for everyone, as each successive vehicle "adjusts" the following distance, thereby continually having the effect of slowing traffic.

Also, what few times I've used it (very few, just to experiment), all it does it open up a space which allows someone to cut in and I "lose my place in line". When the happens over and over and over, it causes the net effect of traveling at a slower pace, and not just for me, but anyone behind me.


ACC is an answer to a question that no one asked. Some "brilliant" engineers thought "hey, we can do something new and unique" without ever stopping to think about the REAL WORLD consequences.
 
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In one experiment, the team filled a lane of traffic with seven identical vehicles -- all running the same ACC system -- with a pace vehicle in front.

Once all vehicles achieved a cruising speed of 50 miles per hour, the pace vehicle quickly reduced its speed by 6 miles per hour.

In a domino effect, each of the following vehicles slowed down more and more dramatically so that, by the seventh car, its speed dropped below the minimum required for the ACC system to operate.

(From the article)


What is your experience? I feel like the ACC in my Accord is worse than my personal driving behavior. But I think the researchers are right: there has got to be a way to implement it that could smooth traffic. I don't think we're there yet, and we may even be making traffic worse.

the acc in mine operates to a standstill, so was that last vehicle backing up?
 
I think adaptive cruise is one of the best things to come about on modern vehicles. I wonder how many people here think negative of it while having little to no experience with it. I don't like lane keep assist however and I have it turned off and I don't need to turn it off every time I start the car.
 
Far too few people use regular cruise control. Why would the addition of distance-based speed setting change that foundational problem?

Lots of drivers have become conditioned that they should be around other vehicles. That leads to trains of people glued to one another's bumpers, usually doing 15 MPH over the speed limit, claiming, "I just keep up with traffic," or drivers lingering directly next to other vehicles or, even worse, in their blind spot. Nobody actually wants to pass anybody or pick a speed to maintain, they just want to go as fast as the people near them.

That type of behavior is what screws up traffic flow, not a cruise control system nobody uses.

Personally, I love ACC but I'm smart enough to understand what it does well and doesn't do well. I turn it off in congested traffic and on surface streets because I know it doesn't work so well. Two-lane with no possible passing and the person in front of you can't seem to pick a speed? ACC saves your blood pressure. Limited-access highway with two travel lanes? Practice proper lane discipline and the only difference is you're not having to manually adjust or turn off cruise control while when approaching slower traffic. Now, if you want to be that guy and hang out in the left lane all day, maybe it's not your thing.

Dismissing ACC because it creates a gap that allows other to cut in seems to be bound in purposeful ignorance that many traffic scenarios aren't congested enough for drivers to behave like that. It's like dismissing pens because ink can't be erased. Of course it can't, that's why pencils exist. Being mad at the pen isn't a very reasonable reaction. Being upset about a vehicle system because people are poor drivers seems kind of backwards.
 
Don’t forget about the wear to the rear brakes as they’re being used to control the speed of the vehicle.
 
I use mine, and personally don't think it brakes or accelerates very aggresively, BUT those "dongles" from Progressive have an entirely different opinion. I'll get a warning on occasion when using that thing. Fortunately, the 6 month period expired, and ended with no discount.
I also don't see it alevieating traffic congestion, and possibly making it worse. As I was on my last road trip, on I95, I put on my left turn signal to pass. No alarm, so I figured left lane was clear, moved to the left and saw another Mercedes behind me hit the brakes fairly hard. I had space, but HIS ACC obviously didn't think so.
 
Don’t forget about the wear to the rear brakes as they’re being used to control the speed of the vehicle.
Really? Why wouldn't it use all four brakes?
Maybe you're thinking of lane keep assist, which uses the rear brakes individually to guide the car back into the lane.
 
I like it for road trips but in daily commute traffic I don’t use it. My Tesla’s is pretty decent but only goes to 85 mph and it does use the brakes at times in stop and go traffic where I’m able to modulate that myself with just the go pedal.

In extreme traffic due to an accident or something it works great and I’ll use it.

I have a bigger problem with people leaving a 5+ car gap in 20 mph traffic between them and the car ahead of them.
 
At the age of 79 I love it. It actually drives closer to the car in front and thats good bc reaction time is zero. I can't understand turning it off. Thats just me. Why would you use cruise WITHOUT ACC
 
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Really? Why wouldn't it use all four brakes?
Maybe you're thinking of lane keep assist, which uses the rear brakes individually to guide the car back into the lane.
Adaptive cruise control uses the electronic rear parking brakes the control speed so that would cause extra wear.
 
I think lkas just uses the electric power steering to steer you back on track
Not on this car. The rear brakes can be applied independently to nearly force you back into the correct lane. Use of turn signals, of course, defeats that.
Same deal with ACC, all 4 brakes are applied to reduce speed. The biggest question for me is, does it turn on the brake lights? I'm not sure, but if it doesn't it could contribulte to a mishap.
 
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At the age of 79 I love it. It actually drives closer to the car in front and thats good bc reaction time is zero. I can't understand turning it off. Thats just me. Why would you use cruise WITHOUT ACC
Years of not having it?

I don’t use cruise much, but have driven highways for a while. Often on autopilot… it’s the same darn road, day in and day out. Anyhow, I have a reflex that kicks in at a few car lengths. I see I’m closing the gap, and its time to move into the left lane and pass. Thing is, with adaptive cruise, it slows down and leaves a gap that doesn’t trigger the reflex. A few miles goes by, I then realize I’m driving slower than my target, realize what happened, change lanes.

It’s not awful but I have not gotten used to it.
 
I love ACC. I've used it in a Ford fusion PHEV and my cx5. The fusion had a much smoother ACC, most likely aided by the CVT for smooth acceleration and battery charge on decel. The cx5's acc gets too close before it starts coasting and if the difference of speed between you and the car in front is greater than 5mph it will have to brake. Both systems will activate the brakes of they are used.

If I'm in the passing lane following traffic or in heavy traffic then I will turn it off because it becomes too jerky and the system brakes really hard if someone cuts in front of you.

It will also work all the day down to a complete stop.
 
In one experiment, the team filled a lane of traffic with seven identical vehicles -- all running the same ACC system -- with a pace vehicle in front.

Once all vehicles achieved a cruising speed of 50 miles per hour, the pace vehicle quickly reduced its speed by 6 miles per hour.

In a domino effect, each of the following vehicles slowed down more and more dramatically so that, by the seventh car, its speed dropped below the minimum required for the ACC system to operate.

(From the article)


What is your experience? I feel like the ACC in my Accord is worse than my personal driving behavior. But I think the researchers are right: there has got to be a way to implement it that could smooth traffic. I don't think we're there yet, and we may even be making traffic worse.
To me, with adaptive, it's pacing the distance as well as speed. You need to leave a cushion and when it slows have enough between you and the car in front to use the cushion to slow vs. slamming brakes on. Adaptive , by leaving the distance constant, slams brakes on. I've read that supposedly the problem is people following too close (with human driving). Then if someone merges or something the entire chain has to "add a car length" like an accordion. If you're leaving a cushion, you don't have to slow as suddenly and it doesn't domino as badly.

My personal hypothesis is that you'd need adaptive to use the pacing distance to slow before slamming the brakes to keep the distance between cars, if that makes sense.

At some point, there are just too many cars and not enough miles of road at certain choke points. I see it in my 30 minute freeway commute every day. If everything else is normal, 3 spots with more merging traffic you can ALWAYS expect the lanes to drop by at least 10-20 mph.

The only real way I can see dealing with that is fully autonomous being able to calculate cars per mile and only merging a certain number of cars per minute...like the stoplights on entrance ramps in larger cities but fully automated.
 
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