# What to do if a rear end accident is imminent. Don’t need answer fast **URL:** \ **Category:** Factual Questions\ **Created:** [February 25, 2021, 3:09am UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702 "2021-02-25T03:09:09Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [February 25, 2021, 7:35pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/21 "2021-02-25T19:35:39Z")
> [@Machine\_Elf](#): > > Applying brakes before the mayhem begins will reduce the total acceleration you experience as your car is rear-ended. Typical consumer-grade passenger car tires are good for approximately 1 G of grip, so that’s the amount by which we’d expect the violence of that first collision (for you) to be reduced. This is a benefit. When this collision ends, your car will have less forward forward velocity carrying you to the next collision, also a benefit. I wonder how much G’s putting it in park gives. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 25, 2021, 7:44pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/22 "2021-02-25T19:44:01Z")
Won’t help. The brakes are strong enough to lock the tires. So the friction that matters is non-rotating tires sliding across the pavement. Adding a locked transmission can’t stop the tires any more than they already are. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [February 25, 2021, 7:55pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/23 "2021-02-25T19:55:15Z")
I assume that in a collision, there isn’t enough time for the ABS to come into play. As far as putting your head firmly against the headrest, this not only eliminates an impact, it also protects from lateral motions if the car comes in at an angle, or you end up getting pushed into cross traffic and hit in the side. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [February 25, 2021, 7:57pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/24 "2021-02-25T19:57:15Z")
Just wanted to say thanks to @Machine_Elf for all the information and links he has provided in this thread. It has been really interesting, a lot of stuff that is not obvious, with at the end of it a pretty straightforward best course of action for an event that will likely actually happen to at least one reader of this thread. ---
**Author:** ![eschrodinger](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschrodinger/32/122_2.png) [@eschrodinger](https://boards.straightdope.com/u/eschrodinger)\ **Post date:** [February 25, 2021, 8:04pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/25 "2021-02-25T20:04:35Z")
> [@LSLGuy](#): > > My attitude in an accident (and especially one I didn’t cause) is “every man for himself”. I’m content to operate my vehicle to minimize the consequences on me and my passengers. If that makes life worse for somebody else, so be it. Trolley problems notwithstanding. If folks don’t like my mid-accident driving they should stay off the sidewalk! 😉 This has been an interesting question in the self-driving car context. In theory, at least at some point, AI “drivers” will be able to calculate optimal actions based on different priorities. The problem is, we as a society don’t currently tend to make explicit or agree on what those priorities are. Like, some people will place greater consequences on anyone breaking the law. Others would always try to avoid hitting pedestrians. And, as relevant to this thread, there could be different solutions for the AI’s optimal actions depending on whether the priority is minimizing total risk of injury vs. minimizing risk to the occupants of that vehicle only. With our ordinary human brains, I think I don’t care about differences based on braking vs not braking – I think it’s largely instinctive anyway, but I would have a problem with someone minimizing risk to themselves by, say, driving up on the sidewalk and hitting a pedestrian. (I get that you weren’t suggesting that.) ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [February 25, 2021, 8:11pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/26 "2021-02-25T20:11:07Z")
Yes, the capabilities of an AI will mean that we really do have to answer some tricky ethical questions akin to the Trolley Problem. Don’t steer into a pedestrian to save your passenger. But what if you are headed for a pedestrian _without_ steering, and the only direction to steer is over a cliff? Two pedestrians…? Of course, one hopes that the whole ridiculously dangerous arrangement of shooting around in independently-controlled hunks of metal that frequently bang into each becomes obsolete, making these ethical conundrums extremely rare. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [February 25, 2021, 8:24pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/27 "2021-02-25T20:24:04Z")
> [@eschrodinger](#): > > > [@LSLGuy](#): > > > > My attitude in an accident (and especially one I didn’t cause) is “every man for himself”. I’m content to operate my vehicle to minimize the consequences on me and my passengers. If that makes life worse for somebody else, so be it. Trolley problems notwithstanding. If folks don’t like my mid-accident driving they should stay off the sidewalk! 😉 > > This has been an interesting question in the self-driving car context. In theory, at least at some point, AI “drivers” will be able to calculate optimal actions based on different priorities. The problem is, we as a society don’t currently tend to make explicit or agree on what those priorities are. Like, some people will place greater consequences on anyone breaking the law. Others would always try to avoid hitting pedestrians. And, as relevant to this thread, there could be different solutions for the AI’s optimal actions depending on whether the priority is minimizing total risk of injury vs. minimizing risk to the occupants of that vehicle only. > > With our ordinary human brains, I think I don’t care about differences based on braking vs not braking – I think it’s largely instinctive anyway, but I would have a problem with someone minimizing risk to themselves by, say, driving up on the sidewalk and hitting a pedestrian. > > (I get that you weren’t suggesting that.) It would be interesting if given the OP and a fully AI car (whatever that means), if the car decided to minimize the impact to the “driver” of said car by realizing that a collision was imminent and started accelerating backwards towards the approaching vehicle. ---
**Author:** ![eschrodinger](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschrodinger/32/122_2.png) [@eschrodinger](https://boards.straightdope.com/u/eschrodinger)\ **Post date:** [February 25, 2021, 8:26pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/28 "2021-02-25T20:26:09Z")
> [@Riemann](#): > > Of course, one hopes that the whole ridiculously dangerous arrangement of shooting around in independently-controlled hunks of metal that frequently bang into each becomes obsolete, making these ethical conundrums extremely rare. Yes. I’m a sceptic on AI driving being anywhere close to being a _safe_ reality, but when it does happen, a huge part of the safety gain will be that they won’t all be independently controlled. I mean, the safest response to a forseeable rear end collision is for all of the cars in the way of the car whose brakes have failed to simply get out of the way in a coordinated fashion, with, perhaps some designated vehicle being used to pace and then gently slow and stop the other car, assuming no other way to safely stop it. That reminds me of the time when I was in the safety patrol as a kid. I worked at a very busy 6 or 8 lanes crossing 4 lanes intersection with an auxiliary Sheriff’s Deputy. One morning, a big semi was blaring it’s airhorn and it barrelled through the red light – brakes out. The deputy jumped in her patrol car, zoomed in front of the semi, and helped get it stopped. It was amazing. Saved some people waiting at the next light, for sure, from being in a nasty crash. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [February 25, 2021, 8:28pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/29 "2021-02-25T20:28:49Z")
> [@eschrodinger](#): > > Saved some people waiting at the next light, for sure, from being in a nasty crash. Until the deputy noticed it was Sandra Bullock driving the rig, desperately waving her arms for the cop to stop slowing her down… ---
**Author:** ![eschrodinger](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschrodinger/32/122_2.png) [@eschrodinger](https://boards.straightdope.com/u/eschrodinger)\ **Post date:** [February 25, 2021, 8:31pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/30 "2021-02-25T20:31:42Z")
> [@Nars\_Glinley](#): > > It would be interesting if given the OP and a fully AI car (whatever that means), if the car decided to minimize the impact to the “driver” of said car by realizing that a collision was imminent and started accelerating backwards towards the approaching vehicle. I’m not seeing how that would be better for the “driver.” Isn’t it actually increasing the energy of the crash for everyone? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 25, 2021, 8:42pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/31 "2021-02-25T20:42:02Z")
> [@eschrodinger](#): > > With our ordinary human brains, I think I don’t care about differences based on braking vs not braking – I think it’s largely instinctive anyway, but I would have a problem with someone minimizing risk to themselves by, say, driving up on the sidewalk and hitting a pedestrian. > > (I get that you weren’t suggesting that.) I disagree with the term “instinctive” although lots of people use it. In an time-sensitive emergency you (any you) will do what you’ve rehearsed. For the vast majority of drivers they’ll have rehearsed nothing so they’ll do nothing. Which mostly means total inaction, but they may well have de facto “rehearsed” that [scary situation → stomp on brakes], so that’s what they’ll do, even if that’s inappropriate for that particular scary situation at that moment. Each of us can choose to think about and rehearse a greater variety of situations and thereby deliver a better performance if/when that situation arises. You may not get it 100% right, but your odds are better with preparation than without. As well, each of us can do a better job of defensive preparation where we reduce the odds of being put into a bad situation. e.g. A simple one is to, when turning left, not turn the car or the steering wheel until you’re clear to proceed through the intersection. Lots of people angle the car or turn the steering wheel so they can get a quicker start around the corner once the opening in traffic appears. But if rear-ended, that geometry forces them head-on into oncoming traffic. That’s dumb. If instead you’re in your own lane facing straight ahead with wheels straight, or even cocked slightly right, then when rear-ended the geometry ensures you’ll be propelled straight ahead or into same-direction traffic instead. Vastly safer outcome that WAG 90% of drivers have never thought about. etc. etc. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [February 25, 2021, 9:00pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/32 "2021-02-25T21:00:21Z")
> [@eschrodinger](#): > > > [@Nars\_Glinley](#): > > > > It would be interesting if given the OP and a fully AI car (whatever that means), if the car decided to minimize the impact to the “driver” of said car by realizing that a collision was imminent and started accelerating backwards towards the approaching vehicle. > > I’m not seeing how that would be better for the “driver.” Isn’t it actually increasing the energy of the crash for everyone? IANAP but I know that in football, I’d rather be moving toward someone that’s about to tackle me instead of standing still. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [February 25, 2021, 9:16pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/33 "2021-02-25T21:16:58Z")
That’s because your forward momentum keeps you from being knocked backwards. Put it this way. Would you rather run into a parked car, or a car that is driving the opposite direction? ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [February 25, 2021, 9:18pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/34 "2021-02-25T21:18:23Z")
Or another way, crashing into a car head on at 30 MPH each is equivalent to crashing into a brick wall at 60 MPH ---
**Author:** ![eschrodinger](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschrodinger/32/122_2.png) [@eschrodinger](https://boards.straightdope.com/u/eschrodinger)\ **Post date:** [February 25, 2021, 9:21pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/35 "2021-02-25T21:21:48Z")
> [@LSLGuy](#): > > I disagree with the term “instinctive” although lots of people use it. Yes, I mean something more like “automatic.” And I agree that what will happen is most likely what you’ve practiced, if anything. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [February 25, 2021, 9:33pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/36 "2021-02-25T21:33:04Z")
> [@Babale](#): > > Or another way, crashing into a car head on at 30 MPH each is equivalent to crashing into a brick wall at 60 MPH No, it’s not. Assuming the same model of cars, a head on crash at 30 MPH is equivalent of hitting a brick wall at 30 MPH. In both situations your car stops instantly and absorbs the same amount of energy. ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [February 25, 2021, 9:49pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/37 "2021-02-25T21:49:56Z")
> [@Telemark](#): > > No, it’s not. Assuming the same model of cars, a head on crash at 30 MPH is equivalent of hitting a brick wall at 30 MPH. In both situations your car stops instantly and absorbs the same amount of energy 🤦‍♂️ good point, twice the energy is delivered to twice the mass resulting in each car experiencing the same amount of energy. ---
**Author:** ![racer72](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/racer72/32/3075_2.png) [@racer72](https://boards.straightdope.com/u/racer72)\ **Post date:** [February 25, 2021, 9:57pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/38 "2021-02-25T21:57:52Z")
> [@Babale](#): > > There was a girl in my hometown who got rear ended like this while driving shortly after getting her license. She made the tragic mistake of looking back at the oncoming car instead of bracing herself against the seat and because of the twisted position her body was in she was killed on impact. Terrible story… so definitely don’t look backwards at the coming vehicle, that’s for sure. My ex wife suffered for years with neck and back problems after doing the same thing. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [February 25, 2021, 9:58pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/39 "2021-02-25T21:58:40Z")
> [@Nars\_Glinley](#): > > I wonder how much G’s putting it in park gives. As noted by LSLGuy, your brakes can already get the tires to skid, so selecting Park won’t make a difference. If you happen to have a two-wheel drive car, it could actually be worse, since then you’d only be locking two wheels, whereas the brakes would lock all four wheels. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 25, 2021, 10:21pm UTC](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702/40 "2021-02-25T22:21:45Z")
Theoretically, you could get better braking by not locking the wheels, so they continue to roll, because then you’re dealing with static friction, which is some amount greater than dynamic friction. But that’s definitely beyond the control capabilities of a mere human. And what I meant by bracing your arms against the seat behind you is to effectively use your arms as more crumple zone. But again, the relative lack of control probably makes this impractical [Previous page](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702.md?page=1) [Next page](https://boards.straightdope.com/t/what-to-do-if-a-rear-end-accident-is-imminent-don-t-need-answer-fast/933702.md?page=3)