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Have you ever looked up stopping distances? https://www.automotive-fleet.com/driver-care/239402/driver-care-know-your-stopping-distance https://www.automotive-

Have you ever looked up stopping distances? https://www.automotive-fleet.com/driver-care/239402/driver-care-know-your-stopping-distance https://www.automotive-fleet.com/driver-care/239402/driver-c... I don’t know how accurate the above is, but it suggest that the stopping distance at 40mph is 5-9 car lengths, so I have to agree with the above poster that if you are routinely leaving one car length and your car system is freaking out, you are probably driving unsafely. Keep in my that statistically this could work out for you fine for 20+ years before one day you get into accident, and presumably blaming the driver who suddenly stopped mid turn. Check out watchpeopledie or idiotsincars for plenty of videos of what could go wrong. I recall one video of exactly this issue — an idiot SUV stopped mid turn in the middle of a lane, clearly a bad driver. And then another driver t-boned her because he didn’t have enough distance to stop, also cleary partially at fault IMO. I know people with lifelong pain from minor auto accidents. Don’t have that be you, or cause that for someone else. What do you lose by keeping some more space between you and the next car?

branon 4y ago
One car length is way more than 15 feet to my mind, probably 40 feet or more depending on speed. See my other comments about how nuanced this entire dialog will inevitably be. Don't you think it's more reasonable to assume we have different definitions of a car length? Perhaps I've used the term in a grossly incorrect manner. "One car length" to me equals "one unit of minimum safe distance taking into account road conditions, traffic conditions, and speed" Not just 15 feet, that'd be insane!
- tshaddox 4y ago
  I think you are confused (either that or I am!). I’m pretty sure a car length is literally the length of a car, which for a Crosstrek is around 15 feet. Given this confusion, it does seem like it explains the root of the disagreement here, but that said, I don’t think it’s unreasonable for people reading your comment to assume that when you said “car length” you meant the length of a car.
- VBprogrammer 4y ago
  You could just admit that you used the wrong term? One car length = the length of a car.
  - branon 4y ago
    Sure, I'm fine with admitting that. It was an inevitable misunderstanding anyway because cars are different lengths so "car length" is largely meaningless. The Subaru's adaptive cruise control system treats car lengths as variable units based on speed. It's much more liberal than I made it sound in the original comment. It sounded reasonable when I wrote it, but infinite nuance strikes again I suppose.
    - foobazgt 4y ago
      Have an upvote for the adaptive cruise control comment. It's this way on the Tesla, too - follow distance is described as car lengths, but it's actually speed-parameterized follow distances in reality. Personally, I find it somewhat confusing, but people should probably be more aware that it's a thing and not necessarily someone mixing up terminology.
- vel0city 4y ago
  > One car length is way more than 15 feet to my mind, probably 40 feet or more Cars in your area are on average 40 feet long? A car length is about the length of an average car. Either way, with a 40 foot "car length", 1-2 car lengths is then ~80 feet. The above stopping distance chart puts a 40mph stopping distance with reaction time at almost 140 feet. <80 feet away is driving way too close at 40mph! Especially for a car you know is doing a maneuver which could result in them braking suddenly such as turning into another field of traffic.
  - branon 4y ago
    With the amount of semi-trucks in my area, actually yes, average length of vehicles you encounter on the road is probably close to that. I just used the term "car length" with entirely too much room for interpretation and am now getting torn apart for it, my mistake. I swear I'm not tailgating people LOL
    - vel0city 4y ago
      > I swear I'm not tailgating people LOL If you're going 40mph and approaching nearly stopped cars at <80 feet, you're absolutely tailgating people and creating extremely risky situations. Don't get me wrong, I've had my emergency braking trigger for similar circumstances of someone turning into a parking lot off a feeder of a highway. But I don't blame my equipment, I acknowledge I'm not a perfect driver. The car knew it could have been quite a challenge to stop in time and so it took action. The better action would have been for me to be going slower and approach that situation with less speed, not to just blame the car for being cautious and forcing realistic safety margins.
      - branon 4y ago
        Nobody's approaching nearly stopped cars, I think you have misunderstood some other facet of my post. I sometimes approach _decelerating_ vehicles, _while I am also decelerating_
        4y ago
- emptybits 4y ago
  > One car length is way more than 15 feet to my mind, probably 40 feet or more depending on speed. A car length is, literally, the length of a car. It does not vary with speed. Exception: https://en.wikipedia.org/wiki/Length_contraction https://en.wikipedia.org/wiki/Length_contraction (coming soon in a software update to a Tesla near you)
  - branon 4y ago
    Sure, but saying this is meaningless when we're actually talking about follow distance. Cars are different lengths. To me, a car length should simply mean the minimum safe _length_ at which to follow the car in front of you.
    - berberous 4y ago
      This would lose all communicative benefits. Teaching a young inexperienced driver “just always keep one car length” where one = safe, is meaningless. I don’t know you, but I believe a majority of people underestimate safe stopping distance. That’s why the webpage I posted, which is one of many similar ones, exist. That’s also in part why there are so many accidents. People are also bad at estimating feet, so telling someone keep 80 feet is also not helpful. But people are pretty good at estimating how many cars can fit between them and the next car. So telling someone, hey, you are tailgating that guy and only one car could fit in front of you, but you need 10 car lengths to be safe, has a lot more communicative power.
      - branon 4y ago
        > Teaching a young inexperienced driver “just always keep one car length” where one = safe, is meaningless. Not if taught correctly, which I think it's important to note that we can't really do via textual communication. In the driver's seat, during a driver's education course, you might learn that a car length is the length of an average car, but you also learn how to count the seconds of stopping distance you have in front of you. In addition, you learn that weather, traffic, and other factors can affect stopping power/distance, the point being that the whole system is incredibly dynamic and variable. One can't reduce a dynamic traffic situation down to "X car lengths = safe." Similarly, saying "1 car length = a safe distance" doesn't really help either. The idea is to teach people what "safety" actually looks like. How it's referred to is secondary. The proof is in how badly I was misunderstood when I said 1-2 car lengths. I _know_ I'm keeping enough distance, because I know how to judge a safe traffic situation. I don't really care what a car length is or isn't, it's fairly irrelevant because safety is a much bigger picture than units of measurement.
VBprogrammer 4y ago
> And then another driver t-boned her because he didn’t have enough distance to stop, also cleary partially at fault IMO. Not partially at fault; completely and totally at fault (except if we're talking about someone deliberately trying to cause a crash in which case I'll settle for partially). The reality is there could be a hundred reasons the car stopped, the driver being an idiot is only one of them. Mechanical failure, something unseen from the following car, a door flying open, someone stepping out in front of them, a queue in front of them which is not obvious from behind etc. If you are not leaving enough room to come to a stop when the car in front does then you are riding your luck, there are no two ways about it.
- giantg2 4y ago
  It sounds like the example was not of a car they were following, but one that pulled out infront of them and stopped in their lane. Just as you are referencing possible excuses for that driver, we could come up with possible excuses for the driver that pulled out (like pulling out suddenly without enough distance to react even if the other car was going under the speed limit). We also need to understand that being at fault isn't 1-to-1 with who was being safe. Typically, if you pull out and get t-boned by someone who has the right of way and is generally following the law, the person being t-boned is at fault for failing to yield. Where a vehicle is impacted plays a huge role in investigators determining who is at fault. Now if you run into the back of the person in front of you, it's almost always your fault, unless the person in front was driving carelessly or recklessly (brake check, for example) but would still involve partial fault in many cases. So really, we can't say either way without knowing a lot more.
yonaguska 4y ago
It's effectively impossible to maintain safe stopping distances in many places. Speaking from experience in Chicago, it's just a concept that doesn't exist for many people. And if you are driving slower in order to maintain a safe stopping distance, you're creating an extra hazard on the road by maintaining a larger speed differential from the rest of traffic. Not to mention, you increase your own risk of accidents because of all the people that will aggressively cut you off. I personally always try to maintain a safe-ish stopping distance, but I'll also ensure that I'm never in a position where I'm missing a swerve ready escape route.
- linuxftw 4y ago
  Little known fact: You can travel the exact speed of the car in front of you while also being any distance N behind them. If I'm traveling greater than 50MPH, I leave at least 3 car lengths between me and them, this is to allow for reaction time to stop at the same rate they are stopping.
  - scruple 4y ago
    In California that just means that in the span of 15 seconds 3 other cars are going to move in front of you and the car that was ahead of you.
    - anikom15 4y ago
      Why does that matter at all? Just slow down to get more space whenever that happens.
- frumper 4y ago
  In my experience they will aggressively cut you off anyway, so you might as well give yourself some breathing room.
eptcyka 4y ago
I don't understand this - are you implying that the only way to safely drive on highways is to always maintain a follow distance equal or greater to your stopping distance? I don't think it's reasonable to prepare for the car in front of you to stop in place as though it had hit a brick wall. Instead, the safe follow distance is derived from the current speed and breaking power of the vehicle I'm operating and the vehichle that's behind me, and the distance to the vehichle behind me.

branon 4y ago

One car length is way more than 15 feet to my mind, probably 40 feet or more depending on speed. See my other comments about how nuanced this entire dialog will inevitably be. Don't you think it's more reasonable to assume we have different definitions of a car length? Perhaps I've used the term in a grossly incorrect manner. "One car length" to me equals "one unit of minimum safe distance taking into account road conditions, traffic conditions, and speed" Not just 15 feet, that'd be insane!

tshaddox 4y ago
I think you are confused (either that or I am!). I’m pretty sure a car length is literally the length of a car, which for a Crosstrek is around 15 feet. Given this confusion, it does seem like it explains the root of the disagreement here, but that said, I don’t think it’s unreasonable for people reading your comment to assume that when you said “car length” you meant the length of a car.
VBprogrammer 4y ago
You could just admit that you used the wrong term? One car length = the length of a car.
- branon 4y ago
  Sure, I'm fine with admitting that. It was an inevitable misunderstanding anyway because cars are different lengths so "car length" is largely meaningless. The Subaru's adaptive cruise control system treats car lengths as variable units based on speed. It's much more liberal than I made it sound in the original comment. It sounded reasonable when I wrote it, but infinite nuance strikes again I suppose.
  - foobazgt 4y ago
    Have an upvote for the adaptive cruise control comment. It's this way on the Tesla, too - follow distance is described as car lengths, but it's actually speed-parameterized follow distances in reality. Personally, I find it somewhat confusing, but people should probably be more aware that it's a thing and not necessarily someone mixing up terminology.
vel0city 4y ago
> One car length is way more than 15 feet to my mind, probably 40 feet or more Cars in your area are on average 40 feet long? A car length is about the length of an average car. Either way, with a 40 foot "car length", 1-2 car lengths is then ~80 feet. The above stopping distance chart puts a 40mph stopping distance with reaction time at almost 140 feet. <80 feet away is driving way too close at 40mph! Especially for a car you know is doing a maneuver which could result in them braking suddenly such as turning into another field of traffic.
- branon 4y ago
  With the amount of semi-trucks in my area, actually yes, average length of vehicles you encounter on the road is probably close to that. I just used the term "car length" with entirely too much room for interpretation and am now getting torn apart for it, my mistake. I swear I'm not tailgating people LOL
  - vel0city 4y ago
    > I swear I'm not tailgating people LOL If you're going 40mph and approaching nearly stopped cars at <80 feet, you're absolutely tailgating people and creating extremely risky situations. Don't get me wrong, I've had my emergency braking trigger for similar circumstances of someone turning into a parking lot off a feeder of a highway. But I don't blame my equipment, I acknowledge I'm not a perfect driver. The car knew it could have been quite a challenge to stop in time and so it took action. The better action would have been for me to be going slower and approach that situation with less speed, not to just blame the car for being cautious and forcing realistic safety margins.
    - branon 4y ago
      Nobody's approaching nearly stopped cars, I think you have misunderstood some other facet of my post. I sometimes approach _decelerating_ vehicles, _while I am also decelerating_
      - 4y ago
emptybits 4y ago
> One car length is way more than 15 feet to my mind, probably 40 feet or more depending on speed. A car length is, literally, the length of a car. It does not vary with speed. Exception: https://en.wikipedia.org/wiki/Length_contraction https://en.wikipedia.org/wiki/Length_contraction (coming soon in a software update to a Tesla near you)
- branon 4y ago
  Sure, but saying this is meaningless when we're actually talking about follow distance. Cars are different lengths. To me, a car length should simply mean the minimum safe _length_ at which to follow the car in front of you.
  - berberous 4y ago
    This would lose all communicative benefits. Teaching a young inexperienced driver “just always keep one car length” where one = safe, is meaningless. I don’t know you, but I believe a majority of people underestimate safe stopping distance. That’s why the webpage I posted, which is one of many similar ones, exist. That’s also in part why there are so many accidents. People are also bad at estimating feet, so telling someone keep 80 feet is also not helpful. But people are pretty good at estimating how many cars can fit between them and the next car. So telling someone, hey, you are tailgating that guy and only one car could fit in front of you, but you need 10 car lengths to be safe, has a lot more communicative power.
    - branon 4y ago
      > Teaching a young inexperienced driver “just always keep one car length” where one = safe, is meaningless. Not if taught correctly, which I think it's important to note that we can't really do via textual communication. In the driver's seat, during a driver's education course, you might learn that a car length is the length of an average car, but you also learn how to count the seconds of stopping distance you have in front of you. In addition, you learn that weather, traffic, and other factors can affect stopping power/distance, the point being that the whole system is incredibly dynamic and variable. One can't reduce a dynamic traffic situation down to "X car lengths = safe." Similarly, saying "1 car length = a safe distance" doesn't really help either. The idea is to teach people what "safety" actually looks like. How it's referred to is secondary. The proof is in how badly I was misunderstood when I said 1-2 car lengths. I _know_ I'm keeping enough distance, because I know how to judge a safe traffic situation. I don't really care what a car length is or isn't, it's fairly irrelevant because safety is a much bigger picture than units of measurement.

VBprogrammer 4y ago

> And then another driver t-boned her because he didn’t have enough distance to stop, also cleary partially at fault IMO. Not partially at fault; completely and totally at fault (except if we're talking about someone deliberately trying to cause a crash in which case I'll settle for partially). The reality is there could be a hundred reasons the car stopped, the driver being an idiot is only one of them. Mechanical failure, something unseen from the following car, a door flying open, someone stepping out in front of them, a queue in front of them which is not obvious from behind etc. If you are not leaving enough room to come to a stop when the car in front does then you are riding your luck, there are no two ways about it.

giantg2 4y ago
It sounds like the example was not of a car they were following, but one that pulled out infront of them and stopped in their lane. Just as you are referencing possible excuses for that driver, we could come up with possible excuses for the driver that pulled out (like pulling out suddenly without enough distance to react even if the other car was going under the speed limit). We also need to understand that being at fault isn't 1-to-1 with who was being safe. Typically, if you pull out and get t-boned by someone who has the right of way and is generally following the law, the person being t-boned is at fault for failing to yield. Where a vehicle is impacted plays a huge role in investigators determining who is at fault. Now if you run into the back of the person in front of you, it's almost always your fault, unless the person in front was driving carelessly or recklessly (brake check, for example) but would still involve partial fault in many cases. So really, we can't say either way without knowing a lot more.

yonaguska 4y ago

It's effectively impossible to maintain safe stopping distances in many places. Speaking from experience in Chicago, it's just a concept that doesn't exist for many people. And if you are driving slower in order to maintain a safe stopping distance, you're creating an extra hazard on the road by maintaining a larger speed differential from the rest of traffic. Not to mention, you increase your own risk of accidents because of all the people that will aggressively cut you off. I personally always try to maintain a safe-ish stopping distance, but I'll also ensure that I'm never in a position where I'm missing a swerve ready escape route.

linuxftw 4y ago
Little known fact: You can travel the exact speed of the car in front of you while also being any distance N behind them. If I'm traveling greater than 50MPH, I leave at least 3 car lengths between me and them, this is to allow for reaction time to stop at the same rate they are stopping.
- scruple 4y ago
  In California that just means that in the span of 15 seconds 3 other cars are going to move in front of you and the car that was ahead of you.
  - anikom15 4y ago
    Why does that matter at all? Just slow down to get more space whenever that happens.
frumper 4y ago
In my experience they will aggressively cut you off anyway, so you might as well give yourself some breathing room.

eptcyka 4y ago

I don't understand this - are you implying that the only way to safely drive on highways is to always maintain a follow distance equal or greater to your stopping distance? I don't think it's reasonable to prepare for the car in front of you to stop in place as though it had hit a brick wall. Instead, the safe follow distance is derived from the current speed and breaking power of the vehicle I'm operating and the vehichle that's behind me, and the distance to the vehichle behind me.