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Small car safety vs large car.
craig1410 - 18/12/10 at 04:09 PM

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.


scootz - 18/12/10 at 04:15 PM

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]


l0rd - 18/12/10 at 04:22 PM

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.


matt_claydon - 18/12/10 at 04:22 PM

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/


ssc28 - 18/12/10 at 04:26 PM

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


matt_claydon - 18/12/10 at 04:32 PM

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.


craig1410 - 18/12/10 at 04:37 PM

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.


David Jenkins - 18/12/10 at 04:44 PM

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.


eznfrank - 18/12/10 at 04:45 PM

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!!!


designer - 18/12/10 at 04:46 PM

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.


scootz - 18/12/10 at 04:48 PM

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!


craig1410 - 18/12/10 at 04:49 PM

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.


eznfrank - 18/12/10 at 05:01 PM

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!!


MikeR - 18/12/10 at 05:06 PM

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


craig1410 - 18/12/10 at 05:13 PM

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.


scootz - 18/12/10 at 05:19 PM

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]


AndyW - 18/12/10 at 05:31 PM

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]


bitsilly - 18/12/10 at 05:35 PM

[Edited on 18/12/10 by bitsilly]


bitsilly - 18/12/10 at 05:36 PM

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]


adithorp - 18/12/10 at 05:38 PM

In the FifthGear crash test the Smart safety cell survived but the deceleration would have liquidised the occupants internal organs.


l0rd - 18/12/10 at 05:49 PM

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.


MikeR - 18/12/10 at 05:58 PM

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)


Rek - 18/12/10 at 06:03 PM

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..."


craig1410 - 18/12/10 at 06:04 PM

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.


matt_gsxr - 18/12/10 at 06:08 PM

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.


britishtrident - 18/12/10 at 06:13 PM

Since when is the MINI a small car.


Just watch the news a lot of the reported fatal head on accidents the fatalities are nearly always in a Punto or Corsa or older Fiesta.


mangogrooveworkshop - 18/12/10 at 06:31 PM

Does the Smart's Tridion safety cell really work for example?


YES MY WIFE WALKED AWAY FROM TWO CRASHES WITH NO INJURIES. SHE WAS CRASHED INTO TWICE REAR AND THE WEE SMARTS CRASH CELL TOOK THE ENERGY AWAY..... IT WAS PANELS AND A CRASH BUMPER TWICE!!!
THE TOYOTA AND THE HONDAS FRONTS WERE TOAST


bmseven - 18/12/10 at 06:49 PM

Interestingly on the safety issue last weeks fith gear were talking about how everyone publishes there 0-60 but no one there 60-0

Partly I guess because there is no standard measurement, but could be included in an ncap type test.

Which compared I believe a Suzuki and a Polo over 12 runs and the Suzuki took 8m longer to stop from 60 which could be 2 car lengths which is scarey

Still prefer my big car when it comes to crashing the crumple zone's in the smaller car


rf900rush - 18/12/10 at 07:15 PM

Mass will play a big part.

Look here LINKY

Just like playing snooker.


loggyboy - 18/12/10 at 07:40 PM

Depends a lot on the age of the car.

IE a big old car vs a new small car would probly fair quite well as its got limited crumple zones and a lot of weight so would just push it out the way. But with good cumples, the new car might do ok too.

A big old car vs a big new car might not manage too well as weighs about the same but having little or no crumple zones would damage the occupants.

a new small car vs a old small car would be similar to the above but maybe not quite as bad as there would be less weight.

a big old car vs a small old car would bound to end in tears for the old car

a big new car vs and old small car would likely be better than the above for the old small car, but still pretty bad.

But its an argument that has too many varibles to give a striaght and accurate answer.

[Edited on 18/12/10 by loggyboy]


craig1410 - 18/12/10 at 08:10 PM

quote:
Originally posted by matt_gsxr
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.


When you say "correct" - what do you think he is correct about?

Do you mean that a Leon would come off better than an Aygo or that all small cars are death traps? The latter is what he believes is the case and this is what I disagree about. I chose my Aygo very carefully and I believe it is a safe and strong vehicle. It certainly feels every bit as solid as a Smart ForTwo for example.


craig1410 - 18/12/10 at 08:13 PM

quote:
Originally posted by MikeR
(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)


No I'm not trying to prove that my car is better than his in a crash, just that driving a small car isn't automatically a bad thing for safety. If you look at my last post it shows that small cars can be better than medium cars in many cases and this data is corrected for road speed/type and age/sex of driver etc. This is explained at the start of the DfT report. By the way, the target demographic for the Aygo is young, new drivers because the insurance is relatively cheap. I find it a brilliant modern substitute for the old BL Mini and is great fun to chuck around on the country roads. It's really good fun on ice and snow too as I have found in the last few weeks!

The laws of physics are one thing, the Euro NCAP tests are another but ultimately the proof of the pudding is in the accident stats and this is what I am looking for. RTA's are so complex that I think this is the only true way to measure the relative safety of each vehicle model.

Cheers,
Craig.


Ninehigh - 18/12/10 at 08:34 PM

quote:
Originally posted by eznfrank
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!!


Well maybe she should put her money where her mouth is and race the biatch. Loser gets to stfu.

As for the OP, you're both kinda right.. A smaller car is probably just as safe when you understeer and hit the tree, but Mr. Range Rover Sport isn't going to notice the bump when he ploughs over a tinbox like an Aygo. Admittedly you'd be less dead than you would be if you was in a (real) Mini, motorbike etc, but you'd be more dead than if you had a similarly sized vehicle.

Problem is because those that just take the kids to school "need" one for the protection of their children (sic) everyone else needs one so they don't get crushed by her


morcus - 18/12/10 at 09:11 PM

I'm with the OP on this one, a modern small car isn't automatically a death trap and it depends entirely on circumstances.
In a head on colsion with another car you'd perhaps come off better in the bigger car but most crashes aren't going to be two cars square front to front.

There is another side to this aswell, if you think your safer your more likely to crash because your more likely to take more risks and pay less attention (in much the same way you see people driving 4x4s around in snow and ice sometimes who assume they should driver exactly like normal, or like some of the stories on here about runflats).

In a modern small car your likely to have a higher seating position so less of you will be underthings that might otherwise crush you.

I'd like to add that all the above is purely oppinion.


craig1410 - 18/12/10 at 09:23 PM

^^^^^

Thanks Morcus.

According to the DfT report near the beginning of this thread, the most likely point of impact for a fatal injury type crash is nearside followed by offside followed by front followed by back.

However for all types of injury the point of contact causing most injuries is back (whiplash) followed by offside, nearside and then front.

I should also point out that these figures are all for TWO car accidents, not single car accidents.


robocog - 18/12/10 at 09:43 PM

I work in a scrappy, been there just over a year now and my conclusion is this

DON'T crash

Seen some stomach churning stuff come through this way and can honestly say I don't think it matters /that much/ what you are in at the time of impact...more what direction the force comes from and how hard the force gets applied

Seen some vehicles you would assume would give you a good chance of survival when needed come in to us and have obviously not quite worked out that way

Stay safe out there

Regards
Rob


MikeR - 18/12/10 at 10:07 PM

Had a very quick read of the document - surprised (and a little impressed) they have tried to account for what i said about different cars driven in different environments.

One thing i did notice which i and others seem to be saying without (previously) any evidence, if you look at the average score for each section (small, medium, large etc), the smaller the vehicle the worse the average score. Its also interesting to note how cars have improved. For example a sierra was rated 5 and a first gen mondeo rated 4. The old rover mini really was a death trap (shame as i loved driving mine).


craig1410 - 18/12/10 at 10:28 PM

quote:
Originally posted by MikeR
Had a very quick read of the document - surprised (and a little impressed) they have tried to account for what i said about different cars driven in different environments.

One thing i did notice which i and others seem to be saying without (previously) any evidence, if you look at the average score for each section (small, medium, large etc), the smaller the vehicle the worse the average score. Its also interesting to note how cars have improved. For example a sierra was rated 5 and a first gen mondeo rated 4. The old rover mini really was a death trap (shame as i loved driving mine).


Yes the larger cars on average have a better score but (and this was my point from the start) there are small cars with better, and in some cases much better, scores than larger cars. The variation WITHIN the group is greater than the variation in average scores across the groups.


Ninehigh - 18/12/10 at 11:24 PM

The Sierra was rated? I thought they didn't start the safety ratings until 2001