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Isn’t this a sign that you are following too closely? A driver should typically be able stop a car length per 10mph. So if you are traveling at 40mph you would

Isn’t this a sign that you are following too closely? A driver should typically be able stop a car length per 10mph. So if you are traveling at 40mph you would need about 4 car lengths to react and stop. Ergo if you are following closer than that you may not stop in time. Just because you are using cruise control doesn’t absolve you of this requirement. My car allows me to set a cruise control gap in seconds which translates to reaction time. 2 seconds is the lowest gap mode and usually leaves me with half the distance necessary for a safe stop (although the car has aggressive brakes and can quickly slowdown at the expense of passenger comfort). Due to this I leave the gap mode at 6 seconds which is larger than I would like but would (and has) allow me to slow down in time for a stopped object in the road. I apologize for any flame wars this creates, since people find driving to be deeply personal and any findings which may criticize their driving habits is generally frowned upon.

mlinhares 2y ago
Following too closely is just how people drive, unfortunately. The main reason I almost always have adaptive cruise control on is so that it keeps me at a safe braking distance from cars in front of me but I've found that most people do not care. Just yesterday there was a corolla that was following a school bus so closely i'm sure it could sniff the bus' ass. That driver was one hard brake away from being decapitated by the school bus bumper.
- bagels 2y ago
  I've used a few adaptive cruise controls that will not maintain a great enough following distance to come to a complete stop in the following distance (eg, in the case that the car in front of you swerves out of the lane revealing an obstacle).
- TylerE 2y ago
  Did that around here and you’ll have people swerving around you.
- seanmcdirmid 2y ago
  The problem I have with adaptive cruise: if you set your gap too wide, usually the suggested gap, people keep swerving into it, so it makes for a very nauseating drive if you are somewhere with not enough traffic that you are moving slowly, but too much traffic that people don't have to change lanes.
  - FeloniousHam 2y ago
    I've found that the adaptive cruise has made me an almost "egoless driver". It does keep a conservative distance, and aggressive drivers do fill in the gap, but I don't care as much when I'm not the one on the pedal. With the full map and destination time in front me, I don't feel the urge to game the system (or maybe I'm just getting old).
  - fragmede 2y ago
    I'm sorry, but can't you just set it to medium or close distance if you're having problems with people jumping into your gap?
    - seanmcdirmid 2y ago
      Ya you can do that, but then it feels like dangerous. When it gets like that I usually just shut it off and control distance myself (and "cough" adjust it to dissuade swerving and then back off for safety).
      - fragmede 2y ago
        ah. my car doesn't have adaptive cruise control but I've rented cars that do. it took a bit to get used to medium and feel comfortable and not dangerous, but then people aren't cutting in.
  - myself248 2y ago
    Sounds like we need adaptive horn control for when people do that.
    - 2y ago
- chefandy 2y ago
  I live in a cramped east coast city. If everyone around here followed the DMV guidelines for distance between cars, morning rush hour would probably be from 4am to 11am. Sure, the fact that everyone's driving in such a tiny little space is the problem, but the infrastructure here doesn't leave us much choice.
  - unglaublich 2y ago
    That's questionable. Flow should improve from increased spacing; it might even offset the density decrease.
    - chefandy 2y ago
      Even if the length of the cars end-to-end is often greater than the length of craggy narrow street between tightly packed but unevenly placed intersections with anywhere from 3 to 8 entry points? Even when all of the 5 highways people are trying to enter and exit– all within the same mile– are all completely backed up? I'd have to see that to believe it.
      - shkkmo 2y ago
        Those seems like situations where extra spacing will help accomodated unexpeded mergings and lane changes without slowing traffic down.
        chefandy 2y ago
        The majority of the roads that aren't highways do not have lanes. The road layout is largely from a hundred or two years before cars existed.
        shkkmo 2y ago
        I fail to see the relevance of this comment?
- nunez 2y ago
  I often try to follow the car-length-per-10mph rule. It's often times not possible. Cars with just duck in front of you and people behind you will pass you. One of many reasons why I hate daily driving.
0xfaded 2y ago
It's a fair point, and at least I think of myself as a fairly conservative driver. I think it is the only time though that I've been faced with a stationary car suddenly appearing where I wouldn't expect one, and that's very different to the car in front needing to slam on the brakes with whom you can share some stopping distance. fwiw 6 seconds at 45mph is 120 meters. That we can comfortably go that far in 6 seconds is a modern marvel, but it's also 20 car lengths.
- grepfru_it 2y ago
  I understand 6 seconds is a lot of space. My cruise control has a delay before reacting so 6 seconds allows for the car to react and if it’s not to my liking then leaves me with the necessary space to stop. On the highway I usually control my distance by switching between 4 and 6 seconds.
  - tjoff 2y ago
    What car is that? Of all the cars I've driven I've never encountered one that allows for more than ~2 seconds on the maximum setting. Thus leaving me a bit nervous. I'm almost hesitant to believe that any car on the market has good enough sensors to do 6 seconds. That is a very long distance at highway speeds.
    - shepherdjerred 2y ago
      I have a Hyundai Sonata that does at least ~4 seconds. It works very well, although it can be annoying when people jump in front of you too closely.
      - tjoff 2y ago
        It has 4 settings, but those don't correspond to seconds https://owners.hyundaiusa.com/content/dam/hyundai/us/myhyundai/manuals/glovebox-manual/2022/sonata/2022-Sonata-OM.pdf https://owners.hyundaiusa.com/content/dam/hyundai/us/myhyund... (page 6-117). Quote: "For example, if you drive at 56 mph (90 km/h), the distance is maintained as follows: Distance 4 - approximately 172 feet" 172 feet at 56 mph is 2.1 seconds. Not saying that you are wrong (maybe a recent model has better cruise control), but I think most people vastly overestimate the adaptive cruise controls in their cars and ~4 seconds would, for reference, vastly outperform 2023 Tesla Y in that aspect.
ethbr1 2y ago
Well, to play the example out... Stopped car in unexpected place. 1 car in front of your vehicle, between you and the stopped car. Assuming the car in front of you switches lanes around the stopped car with 1 car length of space between it and the stopped car. So 2 car lengths + your personal gap for you to slow down. So you could be going no faster than 20mph worst case (0 personal gap). The issue is that the car in front of you doesn't need to stop, so can potentially "suck you in" at an unsafe speed, before you realize you'll need to come to a complete stop (assuming your lane change is blocked).
TylerE 2y ago
It takes FAR more than 50ft to stop from 40mph. I doubt you can even react in 50ft. 40mph is 58 feet per second, so that’s less than a second to Your “rule of thumb” is AT BEST highly misleading. Typical humans take about 250ms to react, and that’s before you actually do anything. There’s 15ft (at least) gone before you even touch the pedal.
- mdekkers 2y ago
  Only a fool breaks the two-second rule: https://en.m.wikipedia.org/wiki/Two-second_rule https://en.m.wikipedia.org/wiki/Two-second_rule
  - lutorm 2y ago
    That rule explicitly states that it's not for being able to stop, though, it's just to have time to react to the driver ahead stopping. Two seconds isn't nearly enough to stop in front of a stationary object. At highway speeds it's even barely enough to not rear-end the vehicle ahead if it has to panic stop.
    - mdekkers 2y ago
      Yep, that’s right. Its a great rule though, and as explained in the article it works at any speed, highway or not. Personally I keep 4 seconds.
mdekkers 2y ago
> I apologize for any flame wars this creates, since people find driving to be deeply personal and any findings which may criticize their driving habits is generally frowned upon. I appreciate your attitude here. Mine is opposite. Dangerous driving injures, maims, and murders both perpetrators and innocents alike. Criticise bad driving loudly and often. You might save lives. I had to tell my mother in law that her daughter, my wife, lost her life in a road traffic accident. There are few aspects to serious road traffic accidents that are not horrific, and speaking up may save lives. Every year, 1.19 million people die as a result of a road traffic accident. Between 20 to 50 million people suffer non-lethal injuries, many of those leading to disability.[1] [1] https://www.who.int/news-room/fact-sheets/detail/road-traffic-injuries https://www.who.int/news-room/fact-sheets/detail/road-traffi...
- CrazyCatDog 2y ago
  Deepest condolences on your loss, and thank you for your candor—I can only speak for myself, but I’m definitely turning up my driving conservatism after reading your post.
- danw1979 2y ago
  I’m very sorry for your loss. I agree with your stance on being vocal about poor driving. People speeding through the 30 mph limit in my village boils my blood like nothing else and I’m one of those parents who shouts at traffic on the school run, even driven by people I know. This has likely cost me a few invitations to the pub but I don’t care.
  - throwaway2037 2y ago
    Can you lobby your gov't rep to install automated camera? It seems reasonable. If you are brushed aside, email/write/call a local newspaper or TV station. They would probably like to report it.
    - macintux 2y ago
      I've seen studies that those flashing speed camera/displays are pretty effective.
Dalewyn 2y ago
>Isn’t this a sign that you are following too closely? If you open enough space ahead of you for a car, someone will cut in. Driving too closely isn't something only you can do something about. In fact, because of the aforementioned behaviour, it's safer to drive too close because it's far more dangerous for a car to cut in in front of you because he perceives "enough" space to do so.
- prmoustache 2y ago
  No it is not safer to drive too close. If someone cuts in front of you, you just slows down a bit to keep enough space and that's it.
lutorm 2y ago
* ... should typically be able stop a car length per 10mph.* This is not correct, stopping distance scales as the square of speed. The distance you'd need to stay from the vehicle in front to be able to stop if it magically came to an instantaneous stop is far, far larger than anyone will reasonably keep. The stopping distance at 65mph, including reaction time, is at least 300ft. That's ~20 car lengths, not 6.5 that your formula would yield. If conditions are wet, your tires are not in great shape, or you're not paying attention, it's going to be much longer.
- stavros 2y ago
  Cars in front don't usually hit walls while they're traveling. It takes a while for the car in front to stop too.
  - Wonton56 2y ago
    But it is possible, when the cosequence is someone dying, the likelihood do not need to be high to act carefully. Anyway the example here was about a car in front avoiding a stopped car.
    - stavros 2y ago
      The thread is about how closely to follow a car. If the car is stopped, the answer is "as closely as you like, it's not moving".
      - Thorrez 2y ago
        This thread is about how closely to follow a moving car. The worry is if the moving car suddenly switches to being stopped. Will you be able to also switch to being stopped before hitting it?
        pixl97 2y ago
        Yea, some people seem to miss that just because the car in front of you can jump over in another lane doesn't mean you can at all. If you have a car beside you, and the car you're tailgating does not, then you're screwed in an emergency situation like this.
deepsun 2y ago
> Isn’t this a sign that you are following too closely? But they said it's FSD who's following too closely. I'd expect automated system should react even better, because it pays attention constantly. That's the whole point, especially when it's called "Full".
- andrewaylett 2y ago
  Unfortunately for anyone relying on so-called "full self driving", that it may be capable of doing much of the driving you remain the driver. It's not even a question of "taking back control". You're expected to be in control of the vehicle.
  - deepsun 2y ago
    There's a lot of technical measures that prevent people doing harmful actions. Even in spaceships, where pilots are highly trained, focused, selected professionals. For example, most cars prevent fiddling too much with its entertainment system while driving, even though drivers are expected to not do that while driving.

mlinhares 2y ago

Following too closely is just how people drive, unfortunately. The main reason I almost always have adaptive cruise control on is so that it keeps me at a safe braking distance from cars in front of me but I've found that most people do not care. Just yesterday there was a corolla that was following a school bus so closely i'm sure it could sniff the bus' ass. That driver was one hard brake away from being decapitated by the school bus bumper.

bagels 2y ago
I've used a few adaptive cruise controls that will not maintain a great enough following distance to come to a complete stop in the following distance (eg, in the case that the car in front of you swerves out of the lane revealing an obstacle).
TylerE 2y ago
Did that around here and you’ll have people swerving around you.
seanmcdirmid 2y ago
The problem I have with adaptive cruise: if you set your gap too wide, usually the suggested gap, people keep swerving into it, so it makes for a very nauseating drive if you are somewhere with not enough traffic that you are moving slowly, but too much traffic that people don't have to change lanes.
- FeloniousHam 2y ago
  I've found that the adaptive cruise has made me an almost "egoless driver". It does keep a conservative distance, and aggressive drivers do fill in the gap, but I don't care as much when I'm not the one on the pedal. With the full map and destination time in front me, I don't feel the urge to game the system (or maybe I'm just getting old).
- fragmede 2y ago
  I'm sorry, but can't you just set it to medium or close distance if you're having problems with people jumping into your gap?
  - seanmcdirmid 2y ago
    Ya you can do that, but then it feels like dangerous. When it gets like that I usually just shut it off and control distance myself (and "cough" adjust it to dissuade swerving and then back off for safety).
    - fragmede 2y ago
      ah. my car doesn't have adaptive cruise control but I've rented cars that do. it took a bit to get used to medium and feel comfortable and not dangerous, but then people aren't cutting in.
- myself248 2y ago
  Sounds like we need adaptive horn control for when people do that.
  - 2y ago
chefandy 2y ago
I live in a cramped east coast city. If everyone around here followed the DMV guidelines for distance between cars, morning rush hour would probably be from 4am to 11am. Sure, the fact that everyone's driving in such a tiny little space is the problem, but the infrastructure here doesn't leave us much choice.
- unglaublich 2y ago
  That's questionable. Flow should improve from increased spacing; it might even offset the density decrease.
  - chefandy 2y ago
    Even if the length of the cars end-to-end is often greater than the length of craggy narrow street between tightly packed but unevenly placed intersections with anywhere from 3 to 8 entry points? Even when all of the 5 highways people are trying to enter and exit– all within the same mile– are all completely backed up? I'd have to see that to believe it.
    - shkkmo 2y ago
      Those seems like situations where extra spacing will help accomodated unexpeded mergings and lane changes without slowing traffic down.
      - chefandy 2y ago
        The majority of the roads that aren't highways do not have lanes. The road layout is largely from a hundred or two years before cars existed.
        shkkmo 2y ago
        I fail to see the relevance of this comment?
nunez 2y ago
I often try to follow the car-length-per-10mph rule. It's often times not possible. Cars with just duck in front of you and people behind you will pass you. One of many reasons why I hate daily driving.

0xfaded 2y ago

It's a fair point, and at least I think of myself as a fairly conservative driver. I think it is the only time though that I've been faced with a stationary car suddenly appearing where I wouldn't expect one, and that's very different to the car in front needing to slam on the brakes with whom you can share some stopping distance. fwiw 6 seconds at 45mph is 120 meters. That we can comfortably go that far in 6 seconds is a modern marvel, but it's also 20 car lengths.

grepfru_it 2y ago
I understand 6 seconds is a lot of space. My cruise control has a delay before reacting so 6 seconds allows for the car to react and if it’s not to my liking then leaves me with the necessary space to stop. On the highway I usually control my distance by switching between 4 and 6 seconds.
- tjoff 2y ago
  What car is that? Of all the cars I've driven I've never encountered one that allows for more than ~2 seconds on the maximum setting. Thus leaving me a bit nervous. I'm almost hesitant to believe that any car on the market has good enough sensors to do 6 seconds. That is a very long distance at highway speeds.
  - shepherdjerred 2y ago
    I have a Hyundai Sonata that does at least ~4 seconds. It works very well, although it can be annoying when people jump in front of you too closely.
    - tjoff 2y ago
      It has 4 settings, but those don't correspond to seconds https://owners.hyundaiusa.com/content/dam/hyundai/us/myhyundai/manuals/glovebox-manual/2022/sonata/2022-Sonata-OM.pdf https://owners.hyundaiusa.com/content/dam/hyundai/us/myhyund... (page 6-117). Quote: "For example, if you drive at 56 mph (90 km/h), the distance is maintained as follows: Distance 4 - approximately 172 feet" 172 feet at 56 mph is 2.1 seconds. Not saying that you are wrong (maybe a recent model has better cruise control), but I think most people vastly overestimate the adaptive cruise controls in their cars and ~4 seconds would, for reference, vastly outperform 2023 Tesla Y in that aspect.

ethbr1 2y ago

Well, to play the example out... Stopped car in unexpected place. 1 car in front of your vehicle, between you and the stopped car. Assuming the car in front of you switches lanes around the stopped car with 1 car length of space between it and the stopped car. So 2 car lengths + your personal gap for you to slow down. So you could be going no faster than 20mph worst case (0 personal gap). The issue is that the car in front of you doesn't need to stop, so can potentially "suck you in" at an unsafe speed, before you realize you'll need to come to a complete stop (assuming your lane change is blocked).

TylerE 2y ago

It takes FAR more than 50ft to stop from 40mph. I doubt you can even react in 50ft. 40mph is 58 feet per second, so that’s less than a second to Your “rule of thumb” is AT BEST highly misleading. Typical humans take about 250ms to react, and that’s before you actually do anything. There’s 15ft (at least) gone before you even touch the pedal.

mdekkers 2y ago
Only a fool breaks the two-second rule: https://en.m.wikipedia.org/wiki/Two-second_rule https://en.m.wikipedia.org/wiki/Two-second_rule
- lutorm 2y ago
  That rule explicitly states that it's not for being able to stop, though, it's just to have time to react to the driver ahead stopping. Two seconds isn't nearly enough to stop in front of a stationary object. At highway speeds it's even barely enough to not rear-end the vehicle ahead if it has to panic stop.
  - mdekkers 2y ago
    Yep, that’s right. Its a great rule though, and as explained in the article it works at any speed, highway or not. Personally I keep 4 seconds.

mdekkers 2y ago

> I apologize for any flame wars this creates, since people find driving to be deeply personal and any findings which may criticize their driving habits is generally frowned upon. I appreciate your attitude here. Mine is opposite. Dangerous driving injures, maims, and murders both perpetrators and innocents alike. Criticise bad driving loudly and often. You might save lives. I had to tell my mother in law that her daughter, my wife, lost her life in a road traffic accident. There are few aspects to serious road traffic accidents that are not horrific, and speaking up may save lives. Every year, 1.19 million people die as a result of a road traffic accident. Between 20 to 50 million people suffer non-lethal injuries, many of those leading to disability.[1] [1] https://www.who.int/news-room/fact-sheets/detail/road-traffic-injuries https://www.who.int/news-room/fact-sheets/detail/road-traffi...

CrazyCatDog 2y ago
Deepest condolences on your loss, and thank you for your candor—I can only speak for myself, but I’m definitely turning up my driving conservatism after reading your post.
danw1979 2y ago
I’m very sorry for your loss. I agree with your stance on being vocal about poor driving. People speeding through the 30 mph limit in my village boils my blood like nothing else and I’m one of those parents who shouts at traffic on the school run, even driven by people I know. This has likely cost me a few invitations to the pub but I don’t care.
- throwaway2037 2y ago
  Can you lobby your gov't rep to install automated camera? It seems reasonable. If you are brushed aside, email/write/call a local newspaper or TV station. They would probably like to report it.
  - macintux 2y ago
    I've seen studies that those flashing speed camera/displays are pretty effective.

Dalewyn 2y ago

>Isn’t this a sign that you are following too closely? If you open enough space ahead of you for a car, someone will cut in. Driving too closely isn't something only you can do something about. In fact, because of the aforementioned behaviour, it's safer to drive too close because it's far more dangerous for a car to cut in in front of you because he perceives "enough" space to do so.

prmoustache 2y ago
No it is not safer to drive too close. If someone cuts in front of you, you just slows down a bit to keep enough space and that's it.

lutorm 2y ago

* ... should typically be able stop a car length per 10mph.* This is not correct, stopping distance scales as the square of speed. The distance you'd need to stay from the vehicle in front to be able to stop if it magically came to an instantaneous stop is far, far larger than anyone will reasonably keep. The stopping distance at 65mph, including reaction time, is at least 300ft. That's ~20 car lengths, not 6.5 that your formula would yield. If conditions are wet, your tires are not in great shape, or you're not paying attention, it's going to be much longer.

stavros 2y ago
Cars in front don't usually hit walls while they're traveling. It takes a while for the car in front to stop too.
- Wonton56 2y ago
  But it is possible, when the cosequence is someone dying, the likelihood do not need to be high to act carefully. Anyway the example here was about a car in front avoiding a stopped car.
  - stavros 2y ago
    The thread is about how closely to follow a car. If the car is stopped, the answer is "as closely as you like, it's not moving".
    - Thorrez 2y ago
      This thread is about how closely to follow a moving car. The worry is if the moving car suddenly switches to being stopped. Will you be able to also switch to being stopped before hitting it?
      - pixl97 2y ago
        Yea, some people seem to miss that just because the car in front of you can jump over in another lane doesn't mean you can at all. If you have a car beside you, and the car you're tailgating does not, then you're screwed in an emergency situation like this.

deepsun 2y ago

> Isn’t this a sign that you are following too closely? But they said it's FSD who's following too closely. I'd expect automated system should react even better, because it pays attention constantly. That's the whole point, especially when it's called "Full".

andrewaylett 2y ago
Unfortunately for anyone relying on so-called "full self driving", that it may be capable of doing much of the driving you remain the driver. It's not even a question of "taking back control". You're expected to be in control of the vehicle.
- deepsun 2y ago
  There's a lot of technical measures that prevent people doing harmful actions. Even in spaceships, where pilots are highly trained, focused, selected professionals. For example, most cars prevent fiddling too much with its entertainment system while driving, even though drivers are expected to not do that while driving.