What to do if a rear end accident is imminent. Don’t need answer fast

Suppose that you are in a stationary vehicle and see that another vehicle is approaching fast from behind. Due to traffic, time, or whatever, you can’t move your vehicle out of the way. What would be the best body posture to assume to minimize damage to your body? I assume that whiplash is the most likely injury. Would pressing my body firmly against the seat and headrest help or just make things worse?

This is exactly the position I instinctively assumed as I watched a car approach and rear-end me in the rear-view mirror in stopped freeway traffic, and another time while stopped for pedestrians. I don’t think there’s be much choice, as your body kind of takes over. Can’t say if it helped or not. It does seem like having your muscles taut would be better than flopping around.

I don’t know but I think it would have to help. Your head being pressed against the headrest would mean it gets shoved forward with the rest of your body, rather than lagging back.

And I believe that at least in part whiplash is caused by your neck muscles not being ready for the sudden movement ie relaxed, allowing your head to flop back then forward, only getting “caught” when your head reaches its end of range of motion, suddenly and forcefully. So I suspect tensing up will cause your muscles to catch and hold your head better.

Make sure hands and arms are clear of where the airbag would deploy?

I instinctively braced my arms against the steering wheel when I saw a rear end crash coming, back when I was a fairly new driver. I was very sore afterward, but no lingering injuries. I suspect with airbags now I’d have at least come away with abrasions on my arms given their positions.

But, yeah, I didn’t get whiplash, even with a pretty energetic crash. I think being pressed back into my seat probably helped.

With your head back there should be less chance of whiplash. Headrests have eliminated most of the worst cases of whiplash, they didn’t used to be standard in cars.

I once acted for a car manufacturer that got sued by someone who drove one of their cars into a brick wall. They were suing for the full thickness friction burns to their thumbs they sustained from the airbag.

They gave up when the evidence showed that (a) there was no way to avoid this from airbags and (b) without the airbag they would mostly likely have frickin’ died!

Some people.

Almost certainly.

In martial arts, there’s the notion of “two hits”. One hit is the person hitting you, the other is you hitting something else. If you’re about to be pushed into a wall, it’s better if you’re already up against the wall. Otherwise, you get hurt by being hit, and get hurt by slamming into the wall.

Similarly, if you’re about to get punched in the jaw, it’s best to have your teeth clenched. That way, your whole head moves as unit, rather than having your lower jaw smashed into your upper jaw, and probably losing a few teeth in the process.

This is highly relevant. When an impact is imminent, your best course of action is to take up all the slack between you and the thing that’s going to be accelerating/decelerating you. In a rear-end collision, that’s the seat back and head rest. This lets the car’s rear crumple zone gradually accelerate you forward, reducing the severity of the impact on your head and body. The alternative is to leave a gap between your body/head and the seat prior to impact, in which case the initial collision accelerates the car forward and then slams the seat into your body.

Some years ago I watched a CART safety presentation from Bobby Rahal. At one point he spoke of how drivers would pull their feet back from the pedals before a frontal impact, believing this would somehow provide a better outcome. Then he showed slow-motion footage from two crash tests - one in which the crash test dummy’s feet were in contact with the pedals before impact, and another in which they were pulled back several inches. In the latter test, the CTD’s feed slammed into the pedals with considerable relative velocity, developing injurious impact forces. The testing showed that it was better for drivers to keep their feet on the pedals if a frontal impact was imminent.

Seat belt tensioners exist for the same reason. Not the long-existing ones that put a gentle tug on the belt at all times - I’m talking about the more recent innovation that very rapidly takes up several inches of slack in the belt during the first milliseconds after an actual frontal impact is sensed. This lets your body decelerate together with the car instead of slamming into the seat belt. Here’s a video demo by the Slo Mo Guys showing how a pyrotechnic tensioner pulls on the seat belt receiver at the moment of impact (the red paint is something they added for visual flair):

I was in a rear end collision several years ago, and interestingly the steering-wheel airbag did not deploy. However, the side airbag did, and I got a decent bruise/scrape on my ribs from it. Like others here, I had plenty of warning and was bracing for impact, cramming my body and head firmly against the seat; other than the airbag bruise, I got through it with no injuries. I know I was using my feet to brace, but I can’t recall whether I was also pushing off of the steering wheel with my arms. I think it’s likely, because my left arm being out of the way is what allowed the side airbag to slap my rib cage.

I think you’re right though: the best bet would be to take your hands away from the steering wheel if you realize an impact is unavoidable. Not always possible though, especially if you’re still trying to control the car to avoid a collision or reduce its severity.

The seat is going to slam into you even if you’re already against it. As for “martial arts experts say”, I’d trust them about physiology about as much as I’d trust tour guides about local history.

You’ll minimize peak acceleration by leaning forward and lightly bracing yourself with your hand behind you. The only reason that might not be ideal would be the differential acceleration between different parts of the body, i.e., whiplash.

I’d rather accelerate forward together with the seat instead of having it (and my car) build up some velocity before it slams into me.

Can’t picture this. Can you explain more about what you’re proposing with one’s hands, and why it might minimize peak accel?

I would also place both feet on the brake as hard as I can, to hopefully prevent the car from plowing into the vehicle in front of it, or into cross-traffic.

I was watching one of the helicopter rescue programs that seem to fill the schedules these days. They turned out to a one-car collision, where the driver had managed to glance off a post and hit a tree at high speed.

The driver was fatally injured. His head had bulls-eyed the windscreen and his chest was crushed by the impact with the steering wheel. From the video, it was clear that he was not wearing a seatbelt and the airbags had not deployed. It was a fairly new car.

This lead me to Google to find out if not wearing the belt deactivated the airbags, and was surprised to discover that this is the case on many modern cars. Apparently, the airbag can make the situation worse for an unrestrained driver.

I think that this feature should be more widely known, as I suspect that some people think that they don’t need to belt up as the airbags will save them.

Advice on how to configure your own car seat to minimize risk of neck injury in a rear-end collision:

Note that all of the advice - seatback angle, headrest height, headrest angle - is geared toward reducing or eliminating the gap between your head and the headrest.

Navy pilots launching from an aircraft carrier face a similar situation: they experience about 3 G of acceleration during the catapult stroke. Per hand signals #7 and #9 on this PDF chart, part of the procedure in the seconds before launch is to assure that each flight crew member has their head firmly back against their headrest to assure that their head accelerates together with the aircraft instead of having the aircraft smack into their head.

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.

In various defensive driving courses we were always advised to take your feet off the break so the car would roll forwards some and utilise the crush zones of the front and back of the car and reduce the acceleration forwards and so lower potential for whiplash. It also had the advantage of getting your legs back out from under the dash and lower chance if legs getting trapped.

We were also told to put car in neutral and switch off engine if at all possible if there was time, which I felt to be a bit optimistic.

Sorry many edits there.

Airbags do not go off when you are rear ended. Been there, done that when I was rear ended by a farm truck going 60 mph. I work for a car manufacturer and brought this up to a friend in the airbag group and he confirmed that they were working as designed.

I took my foot off the brake right before impact and was going to hit the gas when I was rear ended. Threw me into on coming traffic which I fortunately missed. My head moved forward and struck the sunshade so I was taken in to check for a concussion. I was told that this was common in rear end accidents.

In my case, there was a car in front of me, which my car struck from being pushed into it. I don’t clearly recall how hard that impact was, but I assume if it was hard enough, it would have set off airbags, if they had existed.

I’m not sure how fast the rearending car was going, but I was watching them drive right at me in the rearview without noticing I was stopped. They did brake at the last second, but it wasn’t for long.

Unless you are the first car at a traffic light with heavy or fast cross traffic that’s the worst thing to do for yourself. Far better to have your car move easily and crunch into the car ahead. You want to accelerate and decelerate over the greatest distance possible because that reduced the forces on your body as much as possible. The more of your car (and other people’s cars) gets bent, the less total energy ends up inside you.

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.

Assuming there’s a gap between your car and the car in front of you, braking will scrub off more velocity prior to that collision. Also a benefit.

During the subsequent collision between your car and the one in front of you, braking will increase the decel you experience. This is a bad thing, but it’s far less bad than all the above benefits. The most violent collision in this chain of events is the initial rear-end collision, so if the choice is “full brakes throughout the whole sequence” or “zero brakes throughout the whole sequence”, then mitigating the initial rear-end collision by standing on the brakes has higher value than mitigating your collision with the car in front of you by staying off of the brakes. Example, 10 Gs forward followed by 5 Gs rearward is better than 11 Gs forward followed by 4 Gs rearward.

OTOH, braking during the initial rear-end collision makes it worse for the guy who started this whole mess. However, he started this whole mess so maybe you, as the impending victim of his negligence, are entitled to this small act of self-preservation at his expense.

Hmm. I can’t fault the logic. Smells different from the conventional wisdom I’ve read elsewhere. Cue a google-grination and I’ll report back.

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! :wink: