4 ms·

Robocars improve traffic even when most cars around them are driven by people

19 points by gmays 2y ago

foundart 2y ago
It’s a theoretical result, not something happening with current self-driving cars. “Our work is the first to demonstrate the feasibility of controlling mixed traffic via robot vehicles at real-world, complex intersections.”
- xnx 2y ago
  > It’s a theoretical result, not something happening with current self-driving cars. I'm having a hard time finding the specific reference, but Waymo has a solid study showing that the presence of their cars in the areas they operate in became overall safer.
meowster 2y ago
I think it's plausible. I believe a lot of traffic would disappear if people drove the same speed. I do a lot of highway driving and use cruise control, and I see lots of cars go faster, then slow down, then go faster, then slow down, etc, causing more lane changes and probably annoying other drivers. Lane changes takes up two spaces and causes others to slow down creating a domino effect. Traffic is one of those things where if everyone else looked out for each other, waited their turn, let people merge, etc, then everyone would get to their destinations sooner.
- Rebuff5007 2y ago
  There's a group in UT Austin that has spend lots of time trying to model and analyze such dynamics: https://www.cs.utexas.edu/~aim/ https://www.cs.utexas.edu/~aim/
ajuc 2y ago
Only when you ban pedestrians and cyclists. I.e. in a dystopia.
austinheap 2y ago
I feel 100x safer in a Waymo than an Uber in SF. That said I did have a Waymo lose its mind and take me to a random alley in Chinatown at 3am…that was fun.
jonhohle 2y ago
My experience with Waymos is that I am much more cautious around them both out of curiosity, but also because if something does go wrong, I don’t know what signals I have to change their behavior (e.g. honking, polite gesturing, etc.). Once autonomous cars are more common, I wonder if people will relax back to relaxed/sloppy/aggressive patterns. Maybe most already people don’t notice. As an aside, I left a baseball game a few months ago and was surrounded by six Waymos leaving downtown with the game traffic. How wild to see almost the same number of driverless cars as traditional cars. My kids are young enough that they won’t know any different, but from my mid-40s perspective it may as well have been the Jetsons.
greenthrow 2y ago
This is talking about purely hypothetical future robocars that don't exist today. Yes, great. Flying cars would improve traffic too.
Tiktaalik 2y ago
"Optimize" traffic flow all you like it's not really relevant at all because it's not the dominant problem, cannot ever address the fixed spacial constraints of car and road network, and whatever gains are achieved will be instantly swamped by induced demand and the fixed road network. There may be hypothetical efficiencies to be found in a closed network, but that is not real life. In real life people may choose to begin driving or stop driving at any time. We need to be aware of the impacts of people deciding to drive more. In real life as soon as traffic improves and time spent in traffic decreases that is a pricing signal to the market, lowering the time price of choosing to drive instead of other alternatives, and encouraging people to switch to driving vs other alternatives. The amount of traffic will increase again until it reaches the fixed maximum throughput of the road network or the highest price people will pay in terms their time before seeking other alternatives. This is the well studied phenomenon of induced demand. Previously of concern to engineers weighing whether to build a 10 lane vs 8 lane bridge, but also very applicable to this new technology. When we consider that there is a significant amount of people that currently cannot drive that will now be able to drive with the introduction of self driving cars, such as children and the elderly, it's clear that the most likely outcome of prevalent self driving cars will be a significant increase in the amount of cars on the road. This induced demand for driving will necessarily make traffic remarkably worse regardless of whatever marginal optimizations may occur.
- floxy 2y ago
  >When we consider that there is a significant amount of people that currently cannot drive that will now be able to drive with the introduction of self driving cars, such as children and the elderly, Also, I'd expect the average number of people per car to decrease. I could even see the average dipping below one. Just think of things like sending your empty car to the vet, to pick up the dog. Or sending an empty car to Walmart to have them fill your grocery order. Or people who will have their empty car circle around instead of paying for parking (or because there are no parking spots available). And think about how no-passenger cars aren't really going to care too much if they are stuck in traffic.
  - oh_nice_marmot 2y ago
flax 2y ago
I skimmed the article, but the only metric I saw mentioned was that "traffic jams were eliminated". What metrics do the hypothetical robocars improve? I ask because time-to-destination is not the only metric I find myself caring about. I will often choose a much longer, scenic, route instead of the congested highway even though it adds 10 (estimated) minutes to my trip. But I'd rather be actively driving, moving through space and feeling like I'm making progress for an hour than sit in a barely moving queue for 50 minutes.
- pchristensen 2y ago
  This video illustrates the principle: https://youtu.be/iHzzSao6ypE?si=maK5yPJn7LMhPDU1 https://youtu.be/iHzzSao6ypE?si=maK5yPJn7LMhPDU1 Basically, people following too closely cause more braking, which cascades to more braking for an obstacle that was never actually there.
deleted 2y ago
[deleted]
jjk166 2y ago
I can't seem to find the original source, but I read years ago that a surprisingly small percentage (I believe 4%) of drivers just leaving excess headway was sufficient to mitigate most congestion-causing traffic waves. It makes sense to have robots be the ones driving in that counter-intuitive fashion.
- verdverm 2y ago
  I recall another report that most traffic jams could be made much better if people slowed down when approaching and were accelerated their way out on the other side. Makes sense from a basic flow rate / bottleneck perspective, but people will still race around others to late merge 10 cars up and cause everyone to got to a full stop...

19 points by gmays 2y ago

It’s a theoretical result, not something happening with current self-driving cars. “Our work is the first to demonstrate the feasibility of controlling mixed traffic via robot vehicles at real-world, complex intersections.”

xnx 2y ago
> It’s a theoretical result, not something happening with current self-driving cars. I'm having a hard time finding the specific reference, but Waymo has a solid study showing that the presence of their cars in the areas they operate in became overall safer.

meowster 2y ago

I think it's plausible. I believe a lot of traffic would disappear if people drove the same speed. I do a lot of highway driving and use cruise control, and I see lots of cars go faster, then slow down, then go faster, then slow down, etc, causing more lane changes and probably annoying other drivers. Lane changes takes up two spaces and causes others to slow down creating a domino effect. Traffic is one of those things where if everyone else looked out for each other, waited their turn, let people merge, etc, then everyone would get to their destinations sooner.

Rebuff5007 2y ago
There's a group in UT Austin that has spend lots of time trying to model and analyze such dynamics: https://www.cs.utexas.edu/~aim/ https://www.cs.utexas.edu/~aim/

ajuc 2y ago

Only when you ban pedestrians and cyclists. I.e. in a dystopia.

austinheap 2y ago

I feel 100x safer in a Waymo than an Uber in SF. That said I did have a Waymo lose its mind and take me to a random alley in Chinatown at 3am…that was fun.

jonhohle 2y ago

My experience with Waymos is that I am much more cautious around them both out of curiosity, but also because if something does go wrong, I don’t know what signals I have to change their behavior (e.g. honking, polite gesturing, etc.). Once autonomous cars are more common, I wonder if people will relax back to relaxed/sloppy/aggressive patterns. Maybe most already people don’t notice. As an aside, I left a baseball game a few months ago and was surrounded by six Waymos leaving downtown with the game traffic. How wild to see almost the same number of driverless cars as traditional cars. My kids are young enough that they won’t know any different, but from my mid-40s perspective it may as well have been the Jetsons.

greenthrow 2y ago

This is talking about purely hypothetical future robocars that don't exist today. Yes, great. Flying cars would improve traffic too.

Tiktaalik 2y ago

"Optimize" traffic flow all you like it's not really relevant at all because it's not the dominant problem, cannot ever address the fixed spacial constraints of car and road network, and whatever gains are achieved will be instantly swamped by induced demand and the fixed road network. There may be hypothetical efficiencies to be found in a closed network, but that is not real life. In real life people may choose to begin driving or stop driving at any time. We need to be aware of the impacts of people deciding to drive more. In real life as soon as traffic improves and time spent in traffic decreases that is a pricing signal to the market, lowering the time price of choosing to drive instead of other alternatives, and encouraging people to switch to driving vs other alternatives. The amount of traffic will increase again until it reaches the fixed maximum throughput of the road network or the highest price people will pay in terms their time before seeking other alternatives. This is the well studied phenomenon of induced demand. Previously of concern to engineers weighing whether to build a 10 lane vs 8 lane bridge, but also very applicable to this new technology. When we consider that there is a significant amount of people that currently cannot drive that will now be able to drive with the introduction of self driving cars, such as children and the elderly, it's clear that the most likely outcome of prevalent self driving cars will be a significant increase in the amount of cars on the road. This induced demand for driving will necessarily make traffic remarkably worse regardless of whatever marginal optimizations may occur.

floxy 2y ago
>When we consider that there is a significant amount of people that currently cannot drive that will now be able to drive with the introduction of self driving cars, such as children and the elderly, Also, I'd expect the average number of people per car to decrease. I could even see the average dipping below one. Just think of things like sending your empty car to the vet, to pick up the dog. Or sending an empty car to Walmart to have them fill your grocery order. Or people who will have their empty car circle around instead of paying for parking (or because there are no parking spots available). And think about how no-passenger cars aren't really going to care too much if they are stuck in traffic.
- oh_nice_marmot 2y ago

flax 2y ago

I skimmed the article, but the only metric I saw mentioned was that "traffic jams were eliminated". What metrics do the hypothetical robocars improve? I ask because time-to-destination is not the only metric I find myself caring about. I will often choose a much longer, scenic, route instead of the congested highway even though it adds 10 (estimated) minutes to my trip. But I'd rather be actively driving, moving through space and feeling like I'm making progress for an hour than sit in a barely moving queue for 50 minutes.

pchristensen 2y ago
This video illustrates the principle: https://youtu.be/iHzzSao6ypE?si=maK5yPJn7LMhPDU1 https://youtu.be/iHzzSao6ypE?si=maK5yPJn7LMhPDU1 Basically, people following too closely cause more braking, which cascades to more braking for an obstacle that was never actually there.

deleted 2y ago

[deleted]

jjk166 2y ago

I can't seem to find the original source, but I read years ago that a surprisingly small percentage (I believe 4%) of drivers just leaving excess headway was sufficient to mitigate most congestion-causing traffic waves. It makes sense to have robots be the ones driving in that counter-intuitive fashion.

verdverm 2y ago
I recall another report that most traffic jams could be made much better if people slowed down when approaching and were accelerated their way out on the other side. Makes sense from a basic flow rate / bottleneck perspective, but people will still race around others to late merge 10 cars up and cause everyone to got to a full stop...