Question on seatbelt safety

[Talakeal]

The other day I was having a debate with my family about Colorado's rather lax seatbelt laws, when my sister in law told me that someone in the front seat not wearing a seatbelt could easily cause the death of a passenger in the backseat, and for the life of me I cannot imagine how this would happen. The other way around, sure, I can easily see someone in the backseat being launched forward, but not the reverse.

I looked it up, and I found several websites that made this claim, and one that even insisted it was MORE likely for someone in the front to kill someone in the back than vice versa, but none of them explain the actual mechanics of it. I can even find crash test dummy videos of people being thrown forward, but not backward.

The only thing I can imagine would be if you somehow backed into something at great speeds, or maybe where struck head on while stationary or going in reverse, but in those cases I don't see how a seatbelt is going to hold you in place.

Can somebody explain the theoretical mechanics of the physics involved? Or better yet link to a video of a simulation or an article about real case?

Thanks!

[sihnfahl]

Well, yes, it's possible when the individual is in the front seat ends up in the rear due to not wearing a seatbelt.

I'm not talking about the cases where the front seat fails during a crash and it collapses backwards, causing the passenger to slip underneath the seatbelt.

[Talakeal]

Thanks, the video you sent is a good example of what I am talking about. Having trouble visualizing what is actually happening though, it looks like there are multiple impacts and the car flips at some point?

[Rogar Demonblud]

Basically a person not wearing a seatbelt becomes a ballistic object and bounces around until they either come to a rest (often in the back because it structurally sounder) or get ejected via a window. I've had two cousins killed the latter way (one by windshield, the other through the passenger side).

So yeah, always wear the damn seatbelt.

[sihnfahl]

Thanks, the video you sent is a good example of what I am talking about. Having trouble visualizing what is actually happening though, it looks like there are multiple impacts and the car flips at some point?

The guy is swerving after the impact, that's how the vehicle ends up on the side. Lateral movement is why he started moving from side to side, then out of his seat. Car rolls and ... well. You saw the ending.

[farothel]

Basically a person not wearing a seatbelt becomes a ballistic object and bounces around until they either come to a rest (often in the back because it structurally sounder) or get ejected via a window. I've had two cousins killed the latter way (one by windshield, the other through the passenger side).

So yeah, always wear the damn seatbelt.

I can agree with that. I lost a kidney and almost my life (5 minutes longer to the hospital would have been enough) due to becoming a ballistic object inside a car when I was 4 years old (back in the day when there were no seatbelts in the back). With the child seats and seatbelts of today that would have been a few cuts and bruises, maybe a broken rib, but nothing more.

And here in Belgium (and I think Europe) almost all cars are sold with an alarm that beeps when you drive while not wearing a seatbelt in the front. These alarms are really annoying and do not stop (I noticed that when I had a box on the front passenger seat which was heavy enough to trigger this alarm).

So yes, always wear a seatbelt, no matter if the law allows you not to.

[Rogar Demonblud]

Allegedly they're working on upgrading the alarm to not allowing the car to start if the seatbelt isn't worn. Because more and more of automotive safety revolves around not allowing humans to make decisions without supervision.

[Peelee]

I can agree with that. I lost a kidney and almost my life (5 minutes longer to the hospital would have been enough) due to becoming a ballistic object inside a car when I was 4 years old (back in the day when there were no seatbelts in the back). With the child seats and seatbelts of today that would have been a few cuts and bruises, maybe a broken rib, but nothing more.

I was in a pretty bad wreck once, as a passenger. The day after, I had a very dark purplish solid line across my belly and torso which hurt like hell to touch. That lasted about a week. I was also in shock immediately after the accident (shock is way more powerful than I had previously imagined). I had zero other injuries from this wreck, which completely demolished the Toyota Yaris I was in.

I am a very big fan of seat belts, and separately, if I ever meet anyone who was on the engineering team for the Yaris, I will buy them a goddamn beer on the spot.

Allegedly they're working on upgrading the alarm to not allowing the car to start if the seatbelt isn't worn. Because more and more of automotive safety revolves around not allowing humans to make decisions without supervision.

I am perfectly fine with this feature.

[Vinyadan]

This thread has made me reevaluate the advantages of putting my bag in the trunk, instead of leaving it on the passenger's seat.

[Rogar Demonblud]

I tend to put mine on the floor. Accessible yet less likely to become a ballistic object bouncing around the vehicle barring a rollover.

The one time I was in an accident, I got hurt more from the miscellaneous garbage bouncing around the cab than anything else, including a concussion courtesy of a Trapper Keeper.

[Khedrac]

Allegedly they're working on upgrading the alarm to not allowing the car to start if the seatbelt isn't worn. Because more and more of automotive safety revolves around not allowing humans to make decisions without supervision.

I am perfectly fine with this feature.

Oddly enough I am not. Not sure what the current rules are (and I should be, so my next stop will be checking the latest version) but in the UK there used to be exceptions to "driver must wear a seat-belt" rule.
One was in "specially constructed delivery vehicles" (i.e. post office vans there the driver is constantly making very short journeys then getting out again).
Another was "when performing manoeuvers invovling reversing".

The important one here is the second one. Visibility is key when reversing, yet in modern cars rear vision is getting worse. A lot of this comes from the increases in roof strength (for rolling) which makes the rear window pillars bigger (much bigger in some cases) obscuring vision e.g. (every Toyota I have ever driven has had insufficient rear vision). Some cars go for split rear windows (made the first version of the Honda civic with this undrivable for me) presumably for reasons of drag, but it also has a big impact on rear vision.
Wing mirrors are often smaller (reduced drag) and give up space for blind-spot portions (reflect a different direction which I am all in favour of).
Cameras are all very well (my current car has one) but they are very easy to obscure with dirt and even with image intensification they are dodgy in the dark (it's a surprise when I get a good picture in the dark). The can also go wrong (my car is supposed to have a blind spot warning system instead of blind spot mirrors, but it hasn't worked in years and the main dealer cannot fix it).

It's a bit like self-dirving cars - I will start to trust them when I know that they will break the law if necessary, e.g. going through a red traffic light when it becomes obvious that the light is not working.

Edit They have updated the rules:

Exemptions are allowed for the holders of medical exemption certificates and those making deliveries or collections in goods vehicles when travelling less than 50 metres (approx 162 feet).

So the reversing exclusion has been removed - fair enough.

But more importantly I missed the key one - people with a medical exemption are disciminated against if such a rule comes into general force.

Better would be something like the breathalyzer interlock ignition cars - specific cars could be made with the feature for some people, but it not be the standard.
However, the ability to turn round in the seat to physically look behind can resolve most of the risks when reversing, but to do so properly requires the seat-belt to be undone.
I fully support the systems that will beep if the belt is unfastened, but the car needs to be able to drive in this state.

[Peelee]

Edit They have updated the rules:

So the reversing exclusion has been removed - fair enough.

But more importantly I missed the key one - people with a medical exemption are disciminated against if such a rule comes into general force.

Better would be something like the breathalyzer interlock ignition cars - specific cars could be made with the feature for some people, but it not be the standard.
However, the ability to turn round in the seat to physically look behind can resolve most of the risks when reversing, but to do so properly requires the seat-belt to be undone.
I fully support the systems that will beep if the belt is unfastened, but the car needs to be able to drive in this state.

A.) Who updated "the rules"? I assume one of the UK countries, but do you know if UK has federalized road laws across the whole island (and part of the other), or if each country has separate road laws (so if you live in England and read a law for Scotland, it may or may not apply), or what? In the US, people assuming blanket law on specifics is always a dangerous game, since every state has their own laws which may or may not line up with how any other state does it. Don't know about the UK, though. Are you sure that "the rules" as stated are even a monolithic bloc? If yes, fantastic, you're better informed than a lot of people! If no? Might want to find out.
2.) "Medical exemptions" are fun. Do cars with pedals discriminate against people paralyzed from the waist down? There are specialty cars that such people can buy which do accommodate them, but the average Ford doesn't accommodate them and they don't seem to have any issues (I don't know why y'all seem to love Fords so much; my first go-to was Honda). In this hypothetical world of unfastened seatbelts bricking cars, could people with such medical exemptions not need to buy specially-made cars which can turn on without the seatbelt fastened just like any other person with medical needs that are not serviced by standard car production features? More to the point, wouldn't the manufacturers themselves have the onus of determining how best to comply with the law that would otherwise have the potential to get sued to oblivion?

[Vinyadan]

The question I see is, if I am exempt, is it OK that the car will be legally unusable by anyone else in my family? Do they need special permission, too? What about conditions that aren't permanent, like one associated with pregnancy (which isn't ground of exemption in and of itself)?

[Khedrac]

A.) Who updated "the rules"? I assume one of the UK countries, but do you know if UK has federalized road laws across the whole island (and part of the other), or if each country has separate road laws (so if you live in England and read a law for Scotland, it may or may not apply), or what? In the US, people assuming blanket law on specifics is always a dangerous game, since every state has their own laws which may or may not line up with how any other state does it. Don't know about the UK, though. Are you sure that "the rules" as stated are even a monolithic bloc? If yes, fantastic, you're better informed than a lot of people! If no? Might want to find out.

People talk about the UK as if it were a bunch of countries linked together, it's not a good model.

A much better model is that it is a single country (monolithic block) where the government has begun to extend a number of powers down to regional level, mainly to do with taxation and government provided services.
Yes Scotland does have some differences in the legal system, but for things like road safety (which isn't exactly a "service") and the traffic laws things are very much unified. These also mainly date back to the unification so don't cover things like road use.

Also, we have a thing called "Common Law" which is basically established practice, and the judges can rule a published law invalid if it infringes it and wasn't clearly designed to do so, so again the absence of a law doesn't make things legal.

Further, some of the road laws that are enforced do not always turn out to be legally correct! A policement advised me that so far as he knew there isn't a legal 20 mph speed limit in the county! (I don't think he is correct, but I am also confided that the one I live in isn't valid - no repeater signs. On the other hand you probably count for a different road offense if going faster than 20 in most of it.)

The question I see is, if I am exempt, is it OK that the car will be legally unusable by anyone else in my family? Do they need special permission, too? What about conditions that aren't permanent, like one associated with pregnancy (which isn't ground of exemption in and of itself)?

Exactly - it's the edge cases that break rules like this. Once they can answer all of these questions then make the change, but don't make the change first.

Anyway most road law in the UK is combined into a single document "The Highway Code" which all drivers are expected to know (not all is law, but again, if you don't follow it you are probably not driving with due care and attention which is an offense...) It gets re-issued every year but these days I tend to check online as my newset copy is probably at least 10 years old.

It can actually be fun in a quiz - show people some of the road signs they are supposed to know and watch them get it wrong - "No Vehicles" is a good one for that.

[Manga Shoggoth]

Allegedly they're working on upgrading the alarm to not allowing the car to start if the seatbelt isn't worn. Because more and more of automotive safety revolves around not allowing humans to make decisions without supervision.

The point of the alarm is to warn the driver/passenger that they have forgotten to do up their seatbelt. That is all that is needed.

There's no point in setting this up to stop the car from moving unless the seatbelt is worn - That is trivial to bypass as all the system does is detect if the seatbelt is plugged in, not if the seatbelt is going round the person.

[Rogar Demonblud]

In case you haven't noticed, that beeping quits in about 20 seconds. Most people take longer than that getting their current playlist going.

[Peelee]

In case you haven't noticed, that beeping quits in about 20 seconds. Most people take longer than that getting their current playlist going.

Some do. Some don't. It's like turn signal timers, there's no standard.

[Manga Shoggoth]

In case you haven't noticed, that beeping quits in about 20 seconds. Most people take longer than that getting their current playlist going.

I don't even hear it as Iuse seatbelts as a matter of course.

But that is irrelevent, as I was not addressing the bleeping, I was pointing out that changing to "disable the engine" was a waste of time because it is trivial to fool the seatbelt-in-use detection.

[jayem]

Psychologically the idea if immobilising the car makes me very uncomfortable, it makes me think that it would catch people out in some situation where you needed to restart the car quickly.

In rational thought the trolley problems are probably more realistic, as this situation somehow requiring you to be in a position where you are not already wearing a seatbelt, and also where staying the heck away from the car isn't the right thing to do.
None the less my head jumps straight to the person in a stalled car on a level crossing desperately trying to fix their seatbelt.

[The Fury]

Allegedly they're working on upgrading the alarm to not allowing the car to start if the seatbelt isn't worn. Because more and more of automotive safety revolves around not allowing humans to make decisions without supervision.

It doesn't seem like it would be that hard to do. Essentially the seatbelt switch would need to be connected to the PCM which could inhibit the starter circuit, basically the same way a park/neutral safety switch would work.

The only problem is that it's a relatively easy system to trick if you're that determined to not wear a seatbelt.

edit: Do not do this, just wear your seatbelt.

[Keltest]

It doesn't seem like it would be that hard to do. Essentially the seatbelt switch would need to be connected to the PCM which could inhibit the starter circuit, basically the same way a park/neutral safety switch would work.

The only problem is that it's a relatively easy system to trick if you're that determined to not wear a seatbelt.

edit: Do not do this, just wear your seatbelt.

I'd wager that the number of people who dont wear seatbelts out of some sort of malice or petulance is dwarfed by the people who do it out of laziness or apathy. We dont need to make a solution for literally every circumstance, just the more common ones. We cant completely stop people from hurting themselves, but we can at least stop enabling them.

[Telok]

I recall some years ago there were cars with a shoulder strap on a little motorized track in the door frame, one end at the door and one end always locked in, making it a nuisance to avoid being strapped in. Whatever happened to those?

Completely irresponsible but you could put a retractable spike in the steering column that would only retract if the seatbelt was plugged in. All sorts of issues around it of course, but amusing to think about.

[Trafalgar]

I recall some years ago there were cars with a shoulder strap on a little motorized track in the door frame, one end at the door and one end always locked in, making it a nuisance to avoid being strapped in. Whatever happened to those?

Completely irresponsible but you could put a retractable spike in the steering column that would only retract if the seatbelt was plugged in. All sorts of issues around it of course, but amusing to think about.

I had a Ford with this. It had a button you could use to disconnect, which I used about 50% of the time because it was quicker than waiting for the seat belt to go up the track. You still had to manually attach the lap belt though so I feel like it didn't make things a whole lot safer.

[Tarmor]

It doesn't seem like it would be that hard to do. Essentially the seatbelt switch would need to be connected to the PCM which could inhibit the starter circuit, basically the same way a park/neutral safety switch would work.

The only problem is that it's a relatively easy system to trick if you're that determined to not wear a seatbelt.

edit: Do not do this, just wear your seatbelt.

I've been in a few very minor car accidents and one major. My wife has been in one major. (By major, both cars were write-offs that had to be towed away.) We've both avoided serious injury which I feel is mostly because we were wearing a belt. I drive a car and a fork-lift. (Not at the same time!)
Every fork-lift I've seen here won't move unless the seat-belt is connected. Unfortunately, I've seen heaps of people connect the belt, and sit on top of it. In most cases they just don't want to be taking the belt off and putting it back on. (I agree, laziness is the main reason) The same mechanism for a car should be easy, and I support it, even if it's easy to get around.

[JeenLeen]

Another argument I have against seatbelts being needed to operate the car is that that's another point of failure in a electrical system that could disable the car. I could see cases where a car, with expired warranty, has a failure in one part 'talking' to another part, and so it thinks the seatbelt is unbuckled even if it's buckled. That's really unfair to folk with older cars that might 'need' an otherwise unnecessary repair. (I mean, it'd be really annoying to have it constantly beep that your belt is undone, but at least you could drive it.)

I also think of fringe cases. Like you're trying to crank up the car fast because someone is chasing you, and the few seconds to buckle up could matter.

On the other hand, I realize I have an irrational hatred of security features linked to safety, so I try to take my opinions with 'a grain of salt', but I do think that seems a big mistake for rational reasons.

---

Also, in general, I'm a tad annoyed by seatbelt laws due to an anecdote of an incredibly unlikely incident. I use seatbelts every time, but my dad was in an accident where he was driving the car and the driver seat was completely crushed. He wasn't wearing his belt and was thrown out through the front window, which saved his life. (He was in bad shape, but alive.) I realize that, statistically, such an event is incredibly unlikely and he's far safer in general wearing his seatbelt, but the fact that he was in an incident where wearing the seatbelt would have guaranteed his death (as he would have been crushed where it trapped him) makes me dislike them.

[The Fury]

Another argument I have against seatbelts being needed to operate the car is that that's another point of failure in a electrical system that could disable the car. I could see cases where a car, with expired warranty, has a failure in one part 'talking' to another part, and so it thinks the seatbelt is unbuckled even if it's buckled. That's really unfair to folk with older cars that might 'need' an otherwise unnecessary repair. (I mean, it'd be really annoying to have it constantly beep that your belt is undone, but at least you could drive it.)

I also think of fringe cases. Like you're trying to crank up the car fast because someone is chasing you, and the few seconds to buckle up could matter.

On the other hand, I realize I have an irrational hatred of security features linked to safety, so I try to take my opinions with 'a grain of salt', but I do think that seems a big mistake for rational reasons.

---

Also, in general, I'm a tad annoyed by seatbelt laws due to an anecdote of an incredibly unlikely incident. I use seatbelts every time, but my dad was in an accident where he was driving the car and the driver seat was completely crushed. He wasn't wearing his belt and was thrown out through the front window, which saved his life. (He was in bad shape, but alive.) I realize that, statistically, such an event is incredibly unlikely and he's far safer in general wearing his seatbelt, but the fact that he was in an incident where wearing the seatbelt would have guaranteed his death (as he would have been crushed where it trapped him) makes me dislike them.

You're not incorrect, but modern cars have more likely points of failure than that. Not to say that seatbelt switches never fail, (for that matter park/neutral switches,) but I've seen fuel pump immobilizers go screwy much more often.

This isn't to say that having the seatbelt switch able to disable the starter circuit doesn't have problems. There are reasons why you might want to start the engine but not fasten the seatbelt. Say you want to idle the engine for some reason, like maybe you need to get the engine up to temp. Maybe you're trying to move the vehicle to a parking spot in a tight lot and not having the shoulder harness makes it easier to see where you're going.

[The Random NPC]

I recall some years ago there were cars with a shoulder strap on a little motorized track in the door frame, one end at the door and one end always locked in, making it a nuisance to avoid being strapped in. Whatever happened to those?

Completely irresponsible but you could put a retractable spike in the steering column that would only retract if the seatbelt was plugged in. All sorts of issues around it of course, but amusing to think about.

In a word, decapatations.

In more words, people wouldn't use the lap belt and when collisions occurred, problems ensued. Most were only neck injuries, but a couple of people were decapitated.

[Telok]

In a word, decapatations.

In more words, people wouldn't use the lap belt and when collisions occurred, problems ensued. Most were only neck injuries, but a couple of people were decapitated.

Ah, functioning like a hidden death spike then. Well that makes sense. Not like it's the first time people put themselves in more danger by misusing saftey features. People are a problem.

[Vinyadan]

Completely irresponsible but you could put a retractable spike in the steering column that would only retract if the seatbelt was plugged in. All sorts of issues around it of course, but amusing to think about.

I think that's how old cars were made, the centre of the steering wheel was in the prime position to destroy the contents of your breast.

[The Fury]

I think that's how old cars were made, the centre of the steering wheel was in the prime position to destroy the contents of your breast.

Oh yeah. Some even had a pointy horn button. Also, no seatbelts. Totally safe.

Joking aside, some of these did have lap belts. As an option.

edit:

Spoiler: check this out

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