craig1410
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| posted on 18/12/10 at 04:09 PM |
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Small car safety vs large car.
Hi,
Does anyone know where I can get some good statistics on crash safety of small cars versus larger cars? A work colleague of mine is always going on
about how you wouldn't catch him driving a Toyota Aygo like mine because you would have no chance in a crash. He knows nothing about engineering
structures and doesn't understand that just because a larger car has more cabin space doesn't automatically make it safer in a collision.
I would expect that all things being equal, it will be the ratio of space volume divided by structure volume that will be more important. Density if
you like. An extreme example would be where a solid sphere of steel of 750Kg would fare better in a collision with a car weighing 1500Kg. Another
example is an F1 car where they have almost no interior space and yet are very strong indeed.
Now I'm not saying that my Aygo is necessarily stronger than his SEAT Leon and certainly he will have more crumple space and due to laws of
physics will have greater inertia through greater mass which is advantageous in a head on collision with another vehicle. What I am saying is that a
small car is not "automatically" a death trap in the way he thinks it is.
Also, there are many factors which make a given make and model more or less likely to crash (brakes, handing etc.) so what I want to look at is the
overall likelihood for death or serious injury comparing my Aygo with the "average" car or even specifically the SEAT Leon. I believe the
Department for Transport publish a report like this but I can't find it. Maybe you have to pay for it, I don't know. There are also
different types of crash scenario and I doubt that a head-on crash with another vehicle is the most common.
I don't know what the outcome of this might be. He could be right but he is simply basing his opinion on ignorance and assumptions and I'd
like to base my response on something a bit more scientific.
Thanks,
Craig.
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scootz
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| posted on 18/12/10 at 04:15 PM |
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I'm afraid I can't help you with a scientific answer, but on a practical level I can say that I've been to many accidents over the
years and generally speaking, the bigger car has fared better than the smaller car (as has its occupants).
[Edited on 18/12/10 by scootz]
It's Evolution Baby!
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l0rd
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| posted on 18/12/10 at 04:22 PM |
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Depends on the cars.
There is a youtube video a modus vs an old volvo.
I don't know what would happen when 2 new cars colided together but this is why you have the euro crash tests.
A car with 4 stars is a car with 4 stars. It doesn't matter how big it is.
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matt_claydon
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| posted on 18/12/10 at 04:22 PM |
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Some data up to 2004 here. Cars have come along a lot since then though.
http://www.dft.gov.uk/pgr/statistics/datatablespublications/vehicles/carsmmrisk/
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ssc28
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| posted on 18/12/10 at 04:26 PM |
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use this site, you can check the NCAP safety ratings. Try comparing your Aygo against your collegues car, might be interesting.
http://www.euroncap.com/latest.aspx
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matt_claydon
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| posted on 18/12/10 at 04:32 PM |
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quote:
Originally posted by l0rd
A car with 4 stars is a car with 4 stars. It doesn't matter how big it is.
Not true I'm afraid, this is well explained on the EuroNCAP site. The frontal crash test is into a stationary barrier at a specific speed, and
the star rating is based (mostly) on the results recorded by the dummies. The crash energy for the small vehicle is a lot lower than that for the big
vehicle so consequently the small vehicle needs less energy absorption structure to achieve the same test results.
When a big car hits a small one (assuming same age and level of engineering), the small one usually does most of the 'absorbing' as
it's structure was designed to absorb the energy from a 1000kg impact whereas the big one will be made more like the proverbial brick
outhouse.
There are so many more factors that come into play beyone crash engineering, but in simple terms, if you have a head on collision in a 5-star Range
Rover into a 5-star Aygo, the Aygo will come off worse. With cars closer in size and different in age and engineering, the results may not be so
predictable.
Do a google search for 'crash compatibility' and you'll probably come up with lots of information.
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craig1410
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| posted on 18/12/10 at 04:37 PM |
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Hi,
My understanding of the EuroNCap tests is that they are only relevant to cars of the same class. I don't think they account for cars of
different classes (ie. sizes).
Matt, thanks for the link to the DfT document, this is the sort of thing I'm after. It's a shame there is not a more recent report though.
My Aygo isn't in this report although the Yaris is and seems to do quite well.
Scootz, I hear what you are saying and very much appreciate your input. However, I'm not trying to prove that small cars are better than large
cars in a crash because I expect on average that the opposite is true. I'm just trying to prove that there will be exceptions to the rule where
the small car has been built well and the large car has not. The Leon looks like a structurally sound car so I expect it to do well but I think the
same will be true for the Aygo. Either way I would like to know the answer based on fact rather than instinct.
At the end of the day if an Aygo and Land Cruiser were to come together head on, I'd rather be in the LandCruiser but I'm interested in
seeing some exceptions to the obvious. Does the Smart's Tridion safety cell really work for example?
Thanks to all, keep the comments coming in. ;-)
Craig.
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David Jenkins
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| posted on 18/12/10 at 04:44 PM |
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Some TV program (5th Gear?) drove a Smart into a concrete block at a significant speed (60mph or so) and the general opinion was that the occupants
would be hurt, but that they would have probably survived the massive impact. For example, their legs were unlikely to have been crushed, the
steering column wouldn't have speared the driver, and so on.
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eznfrank
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| posted on 18/12/10 at 04:45 PM |
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If he/she is not particularly interested in cars I doubt all the stats in the world will help your argument - some people just won't listen. A
girl I work with insists her Mazda RX8 will cane my ZX12 Indy because her's is a 2.6 litre and mine is only 1.2 litre!!!
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designer
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| posted on 18/12/10 at 04:46 PM |
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Size has nothing to do with safety.
The tiny Smart is one of the safest cars on the road in a collision at 70mph. On impact all the body panels disintegrate while the safety cell remains
intact.
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scootz
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| posted on 18/12/10 at 04:48 PM |
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quote:
Originally posted by eznfrank
If he/she is not particularly interested in cars I doubt all the stats in the world will help your argument - some people just won't listen. A
girl I work with insists her Mazda RX8 will cane my ZX12 Indy because her's is a 2.6 litre and mine is only 1.2 litre!!!
Hers is officially a 1.3!
It's Evolution Baby!
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craig1410
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| posted on 18/12/10 at 04:49 PM |
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quote:
Originally posted by designer
Size has nothing to do with safety.
The tiny Smart is one of the safest cars on the road in a collision at 70mph. On impact all the body panels disintegrate while the safety cell remains
intact.
Exactly my point but I need stats to back this up.
The Aygo is described by Toyota as having a Crash Resistant Body Structure made from high tensile steel which sounds much the same as the Smart. I
think Smart have made this a marketing point specifically to make people more comfortable about crash safety in what is a very small car. The Aygo
isn't quite as small as the little Smart ForTwo so Toyota probably don't need to go quite as far as to make up a name for it and paint it
a different colour.
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eznfrank
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| posted on 18/12/10 at 05:01 PM |
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quote:
Originally posted by scootz
quote:
Originally posted by eznfrank
If he/she is not particularly interested in cars I doubt all the stats in the world will help your argument - some people just won't listen. A
girl I work with insists her Mazda RX8 will cane my ZX12 Indy because her's is a 2.6 litre and mine is only 1.2 litre!!!
Hers is officially a 1.3!
That's exactly what I said - fell on deaf ears!!
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MikeR
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| posted on 18/12/10 at 05:06 PM |
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quote:
Originally posted by l0rd
Depends on the cars.
There is a youtube video a modus vs an old volvo.
I don't know what would happen when 2 new cars colided together but this is why you have the euro crash tests.
A car with 4 stars is a car with 4 stars. It doesn't matter how big it is.
I'd tripple check that last statement.
A friend works for an engineering company and for a while was seconded to a motor manufacturer designing airbags. They said that the euro ncap is not
comparable between classes. A 4 star "small" car is not compariable with a 4 star "executive" vehicle. It basically comes down
to small car much better in a crash involving only the small car as less momentum (esp if you end up on the roof as no car has a great roll over
structure - this is what prompted the conversation after i'd been in a car that rolled). Large cars are better in crashes with small cars as
there momentum is huge compared to the little car thats designed to cope with little car momentum.
In fact, just found this on the euro ncap site,
"Euro NCAP’s frontal impact test simulates a car crashing into another of similar mass and structure. In real life, when two cars collide the
vehicle with the higher mass has an advantage over the lighter one. Generally speaking, vehicles with higher structures tend to fare better in
accidents than those with lower structures. Therefore, ratings are comparable only between cars of similar mass and with broadly similar structures.
Euro NCAP groups cars into the following structural categories: passenger car, MPV, off-roader, roadster and pickup. Within each of those categories,
cars which are within 150kg of one another are considered comparable."
So you can't compare vehicles with greatly different mass /
structure.http://www.euroncap.com/Content-Web-Page/0f3bec79-828b-4e0c-8030-9fa8314ff342/comparable-cars.aspx
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craig1410
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| posted on 18/12/10 at 05:13 PM |
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Mike,
Yes I mentioned that a couple of posts ago and I know about conservation of momentum and conservation of energy laws etc. However, I still think it is
possible for a small car to fare well in a crash with a larger car if well designed. The energy/momentum difference will certainly mean that in a
head-on collision the small car driver will experience more G forces which is not good but this alone doesn't imply greater injuries. Also, as I
mentioned earlier, a head on collision is probably not the most common form of accident.
If I can find statistics showing death or serious injuries for recorded vehicle accidents by make and model then I think I will get the answer
I'm looking for. The link that Matt posted earlier was very close if I could just get an updated version of this report I think that might
satisfy my needs.
Thanks,
Craig.
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scootz
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| posted on 18/12/10 at 05:19 PM |
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quote:
Originally posted by designer
Size has nothing to do with safety.
The tiny Smart is one of the safest cars on the road in a collision at 70mph. On impact all the body panels disintegrate while the safety cell remains
intact.
This is where it all goes awry... yes, the Smart has good results on the automotive industry tests. That's because it was cleverly designed to
do well in the automotive industry tests!
These tests do not allow for the 'vagaries' of real-world accidents.
The reality is that when a car meets a car, they both get damaged. Differing models will damage differently, and each car will shove metal into the
other with a different load behind it and at different angles. The smaller car has less space from front to back, side to side and floor to roof (in
general), so naturally the damaged parts of the larger opposing vehicle will have to travel a shorter distance to penetrate the cabin of the smaller
car (and vice-versa). Add the 'mass' issue to this and the smaller car is (generally speaking) onto a loser!
Again, this is assuming that both cars are comparatively aged.
[Edited on 18/12/10 by scootz]
It's Evolution Baby!
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AndyW
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| posted on 18/12/10 at 05:31 PM |
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quote:
Originally posted by David Jenkins
Some TV program (5th Gear?) drove a Smart into a concrete block at a significant speed (60mph or so) and the general opinion was that the occupants
would be hurt, but that they would have probably survived the massive impact. For example, their legs were unlikely to have been crushed, the
steering column wouldn't have speared the driver, and so on.
You will find the smart car test here: lindy dinky crash
[Edited on 18/12/10 by AndyW]
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bitsilly
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| posted on 18/12/10 at 05:35 PM |
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[Edited on 18/12/10 by bitsilly]
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bitsilly
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| posted on 18/12/10 at 05:36 PM |
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I'd like to back up what Scootz said.
Cars that do well in NCAP are designed to do well in NCAP specific tests, and those tests are very specific regarding speeds and offset to target
etc.
NCAP is a step in the right direction, but would you rather be in a car with many safety features deduced from the real world, or in a car that was
designed to do well with NCAP?
[Edited on 18/12/10 by bitsilly]
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adithorp
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| posted on 18/12/10 at 05:38 PM |
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In the FifthGear crash test the Smart safety cell survived but the deceleration would have liquidised the occupants internal organs.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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l0rd
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| posted on 18/12/10 at 05:49 PM |
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Yes indeed my bad. My point was based on the fact that at 40mph both cars will do well.
Now, take an Aygo and crash it on a Leon at 60mph then the Leon will be better.
Take a Landrover and crash it on a Truck, the truck will come out better.
After all, the Aygo and smart and the rest are city cars where speed is supposed to be low.
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MikeR
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| posted on 18/12/10 at 05:58 PM |
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quote:
Originally posted by craig1410
Mike,
Yes I mentioned that a couple of posts ago [bits deleted]
If I can find statistics showing death or serious injuries for recorded vehicle accidents by make and model then I think I will get the answer
I'm looking for. [bits deleted]
(sorry for repeating what others said on my initial response - slow typing)
What are you trying to achieve as whilst i can see what you're trying to do i don't think the stat's will answer your question.
I think you're trying to prove your car is as safe / safer than your collegeaues using the stats. Now generalising your toyota will be mostly
driven around town, low speed, probably by house wives / house husbands possibly with children and therefore even slower (if my friends attitude with
kids on board is anything to go by) and all reported accidents will be around town at low speed etc. Your collegeaues car will generally be driven in
a different environment, faster etc and all accidents will be different speed etc.
If you drive your small car in the large car environment, there is no guarentee it will survive the accident as well as the stat's suggest as
they're from a different type of driving. I would suggest (with no evidence) that your collegeaues car driven in the small car environment would
fair better than its stats suggest due to being lower speed etc.
(nb, i've got no engineering qualifications but have been a passenger in both a clio and avensis as they were crashed)
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Rek
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| posted on 18/12/10 at 06:03 PM |
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There's also a case to be made for road presence, big v small (ask any two wheeler). I wonder if there's stats for ratios of say.. Big
exec, 4wd, City car that are involved in accidents per number on the road. caused by stuff like "smidsy" and "actually I did see you
but I have a safe big car so i cut in/pulled out anyway..."
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craig1410
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| posted on 18/12/10 at 06:04 PM |
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Looking in a bit more depth at the link to the DfT document Matt posted and I think it is very interesting. Here are a few examples:
Chances of sustaining fatal or serious injuries in an "injury" crash (%)
Some bad small cars:
Rover Mini 14%
Matiz 10%
Panda 10%
Micra (90-92) 10%
Swift 10%
Some good small cars:
Citroen C3 3%
Merc A class 4%
VW Polo 4%
Yaris 5%
Ka 5% (Probably the closest car here to the Aygo in terms of design)
Corsa 5%
Clio 5%
Mini 5%
Some bad medium cars:
Honda Civic (Pre '90) 9%
Peugeot 309 9%
Daewoo Lanos 8%
Hyundai X2 8%
Proton 8%
Maestro 8%
Some good medium cars:
Citroen Xsara 3%
Audi A3 4%
Focus 4%
Hyundai Accent 4%
Nissan Almera 4%
Toyota Corolla 4%
VW Beetle 4%
VW Golf 4%
So this shows that there is more variation within the classes than there is between them. The average small car had a 7% chance of DoSI compared to a
6% chance in the medium/small car.
Unfortunately these figures are looking at some quite old cars so the results for more modern cars might show a different pattern. If anything though
I would expect that small cars will probably perform comparatively better than larger cars today because safety systems previously only fitted to
larger cars such as ABS, EBD, ESP, door bars, Airbags etc. Are now required as standard to all classes of car.
Some interesting results at the 4x4 end of the report too with the Toyota Land Cruiser showing just a 1% chance of DoSI. Again though it is not the
case that all 4x4's are safer because the Honda CRV had 6% and the Ford Maverick and RAV-4 had 5%
Well worth a read.
Thanks,
Craig.
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matt_gsxr
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| posted on 18/12/10 at 06:08 PM |
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I think your colleague is correct.
Its your momentum argument which is always going to result in the lions share of the G forces being doled out to the lighter car.
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