Small car=Deathtrap? Your opinion?
 

What are your guys thought on driving small compacts vs small crossover/suv? Is it worth the extra saving in your wallet but to risk safety?
Obviously larger cars will fair better in a crash vs a small car but are they worth the extra $$$+Gas, Opinions?

http://www.youtube.com/watch?v=cu95gB04VC4

There is always someone bigger than you, even though I drive a big vehicle, safety is not the reason for me, in the past I have generally driven smaller vehicles.
But if I was buying a vehicle for my partner and child, then safety would be the first consideration.
So not always easy to answer a simple question.

This is true for sure.

Personally, I'd hate to make any decision purely based on fear. Drive any car that you feel is basically safe (i.e., fully functional and not falling apart) and let your driving skill and awareness keep you safe.

If a compact would suit your needs feature wise and you wanted more safety, then a large sedan would be a better choice than a crossover/suv. You'd have better safety in a crash, and you'd also retain maneuverability and resistance to rollover.

Safety vs $ is one thing ... but that is not the same as safety vs size ... or safety vs weight.

This is a common but I find at best misleading , and generally speaking incorrect initial assumption... even if it is shared by many people.

There are four other sides of this size/weight vs safety issue , most large vehicle advocates skip... and when looking over the whole issue ... I think in general small and light is safer than large and heavy.

#1> Someone is always bigger/heavier than you.
As others have said car vs car ... me buying bigger does not = me being safer. Unless you are going to avoid the roads that allow any bigger vehicle, the car vs car safety idea is faulty ... limited to roads that don't allow RVs and U-Hauls makes ones driving options extremely limited.

#2> The bigger / heavier vehicle is more dangerous to everyone else around it.
It posses a larger risk to pedestrians, to pets, to property, and in car vs car head on collisions those smaller cars ... or said another way ... choosing to buy bigger/heavier = choosing to put everyone and everything around you in greater risk.

#3> There are other types of accidents than head on car vs car.
Any accident involving hitting a stationary object the heavier car is less safe than the lighter car. It brings more energy into the collision. The human body has the same injury from force tolerances no matter the vehicle. This forces the heavier vehicle to be less safe than the light vehicle. Assuming otherwise equal technology F=ma. If A have superior technology to B that is about the technology not the size or weight.

#4> The heavier vehicle is more likely to get in an accident in the first place.
It's inertia ... the heavier vehicle's greater inertia reducing it's ability to brake to a stop or turn a tight corner to get out of the way... or course there are some technologies that can directly target braking and cornering ... and it is possible specific vehicle A might have some of those while specific vehicle B does not ... but that is about those technologies , and does not change the fundamental issues of greater mass and inertia ... the smaller lighter vehicle with those same level of technologies will always out-corner and brake shorter than the heavier vehicle.

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So as I see it the less $ aspect is a bonus on top of being more safe.

I remember going to a salvage auction where they sell totalled vehicles. The were 3 of the Toyota Land Cruisers there, or 1% of the total number of vehicles sold. All 3 were rollovers.
Not sure what the percentage of Land Cruisers is of the vehicle population but I am sure it's a heck of a lot lower than 3 of 300 or 1%.
Of course this does not even consider motorcycles.
The key to survival in any vehicle is knowing your limitations and situational awareness.
Take a 1 mile square slab of concrete. You have a Greyhound bus and I have a Turbo Carrera Porsche.
Do you think you would have any chance of hitting me intentionally in a bus versus Porsche contest?
Not a prayer.

regards
Mech

The wife drives a SUV (if you want to call it that). She is willing to sacrifice some mileage for better visibility and greater mass. To mitigate the cost of fuel we got the best mileage vehicle we could buy.

3800 pounds 32 MPG highway.

regards
Mech

If you drive a lot of highway, why not buy a used large car with good fuel economy?

Larger cars, at least here in Europe, depreciate faster, and get similar if not better mpg on the highway, so the cost of ownership is comparable to a smaller car and you get the space, comfort and safety along with it. They are also much more stable at speed because of better aerodynamics and longer wheelbase, so the active safety component is also better.

Let's not forget the importance of speed. KE = 1/2 M x V x V "KE" = kinetic energy "M" = mass and "V" = velocity.
So would you slow down to be safer?

if safety is your primary concern then search "traffic safety facts" and be done with it...

Mark Twain had something to say on this:
Or if you want the science, see e.g. Wenzel & Ross: "The Effects of Vehicle Model and Driver Behavior on Risk"

See that the thing here in Ontario, if someone owns a large suv most (not always) they are the more calm driver (trying to save more fuel or just the fact the suv is slower) and they drive more safely, not the hothead in his small manual coupe.

And there's the cost factor that a large car here is almost twice the price of a small one (yes I know it depends) so your not going to be getting inexperienced first time drivers in massive suv's.

I actually see the opposite behavior here. Those with bigger vehicles tend to try and bully their way down the road, whether it be merging into gaps that are too small or refusing to let other cars onto the road.

And in terms of speed, I get passed on the freeway (by an excessive margin I might add) by SUVs just as often as I do by Camrys and Priuses. I'm sorry, but 80-90 mph is not a safe, slow speed for a Tahoe, Navigator, Excursion, Escalade, Hummer, Armada, Sequoia, etc. But they drive that way anyway.

If you keep aware of whats going on around you , a small car is also a smaller target, and
can likewise avoid messes w quick evasive moves in tighter places!

I certainly think the poll shows a general preference: smaller rigs usually handle better, and are more fun to drive!

Anyone who is too chickenisht to ride in a small car is also too chickenisht to get on any two-wheeler of any sort; use stairs or a bathtub; eat cheeseburgers and Doritos; or leave the house.

It's about the car's design, not the car's mass. A heavier car absorbs more impact energy into the structure, and I imagine in side impact situations having the door give away more could be troublesome.

You have it backwards.

F=MA
or
Kinetic Energy = 1/2MV^2

Under the same deceleration ( say you hit a stationary object ) or the same initial speed ... the more mass you have the more impact energy you have. Mass increases the impact energy not decreases it... Mass doesn't absorb the impact energy , it increases it.

A better design is a better design ... that part I'll give you ... but the mass part you have backwards.

I know a semi-driver who was hit by another semi and will be a vegetable for the rest of his life. So much for the large vehicle arms race, when you get screwed even at the very top.

Unfortunately, the data doesn't support your thinking. See the Wenzel & Ross paper, and particularly the differences between body-on-frame SUVs and unibody designs.

I also think you need to get over this fatalistic "I'm going to be hit by another car no matter what, so I'd best carry around a ton or two of armor to protect me" attitude. A good course on defensive driving weighs nothing, and will do more to protect you & your passengers than any amount of added mass.

I love the way Frank simply lays it out!

If we worried ourselves to death about every little thing, we wouldn't have much of a life!

I've thought more than once about giving up motorcycles. But the enjoyment I get back from them is near the focal point of who I am to myself!


Yes, I know I have no protection in the natural realm of things, but if I go that way; it will have been something special to me! (a life w riding in it!)

I still shudder when I'm 5 car lengths from a stop sign w a blind hedge to the right; and a bimbo turns left off a highway totally cutting the blind corner, so if I'd been 1 second faster, and splattered oncoming like a bug!

I have seen the same thing. I saw the aftermath of a empty semi tanker that hit a small box truck from behind on the highway. The box was severely damaged but the cab was fine. The tanker was a different story. The cab parted ways with the frame and was nearly unrecognisable. I don't believe semi driver survived.

In 5 plus years as a traffic spotter, I see roll-overs every day. Three of them have been small cars.

That video showed me there are good and bad small cars. The Yaris got smashed, but that's an older model car. The new model Fit held up amazingly well against the Accord. The Smart... held its structure but got thrown so far as to almost guarantee a secondary impact.

The obvious answer they're trying to tell us is, buy the Camry or Accord. My conclusion is different: buy the Fit. You get the advantages of a small car and reasonable safety.

I said energy absorbed INTO the structure, rather than transferred kinetic energy.

Hmmm I guess. I also forgot that SUVs tend to be a lot higher and so the strength of the doors is less relevant since you'd be getting hit closer to the frame. My bad.

Impact energy is the transfer of Kinetic energy ... they are not separate or different things.

You credited a larger mass itself for absorbing more impact energy:
Which is still incorrect.

It is the design of the structure that would allow it to absorb or not absorb the energy of the impact.

More mass itself ... will ALWAYS increases the energy of the impact ... mass itself does not absorb impact energy it adds more impact energy to the event.

Two vehicles of identical design expect Car A weighs more than Car B ... both vehicles experience the same collision event with a stationary object at the same speed ... Car A with it's greater mass will have more impact energy than car B ... This is just the way the world works ... KE=1/2MV^2 and F=MA ... A heavier , more mass itself always equals more energy and more force... what you wrote about heavier absorbing more impact energy ... is backwards.

A good design can sometimes compensate for the mass penalties ... but that design benefit does not change the penalties of the greater mass ... the design benefits try to overcome or compete with the penalties of greater mass.

I'm thinking of the future in mind when i say this. If everybody drove really light cars under 1500 lbs as i think we will have to do in the future, then i suppose it would be safer overall. I would think that two 1500 lbs cars colliding head on would experience less G's in deceleration as the crumple zones don't also have to absorb an extra 2000 lbs or more mass. A future low mass vehicle would be designed to hold structural integrity and not implode. A low mass vehicle also doesn't necessarily have to be small, It can take up the space of a larger car giving it a larger crumple zone. More of the mass could be designed into safety features instead of just relying on the "dead weight" of 1000 more lbs to save you.

As far as hitting a legitimate source of weight on the highway such as a commercial truck or tractor trailer, weight will not save you up to a point. A lighter car would be more manueverable and brake faster avoiding head on collisions easier which would be much safer overall. Less accidents, safer low impact accidents, safer pedestrian accidents. Overall just much safer across the board compared to the marginal improvement of safety a higher mass vehicle offers in certain situations, and then that is only for you.

The best thing you can do is just buy a car with a good crash rating. A compact car today is much safer than a compact of the same size and weight from the 80's. It's not the weight, it's crashworthiness designed into it

The biggest problem i see with those mini city cars in the video is that they just dont have enough of a crumple zone in the front! That is a design liability, and i do disagree with them being that short. You can have the same mass and add 3-4 feet to that car in length and it would be much much safer. Furthermore your mpg would get much higher. More length doesn't add to the area of drag and it'll improve aerodynamics so much like the Aero civic. Ecomodding Boat tails and bullet nose extension are good for gas and safety! Get with the picture car manufacturers!

But as we keep trying to tell you, you're still stuck in the attitude that the only thing that matters for safety is what happens when your car gets hit by another car, when the point is to avoid being hit (or hitting something, rolling over, etc) in the first place.

I agree with you on #1 and 2.
Your #3 argument seems to make sense until it contradicts itself. More energy in the car or in the passenger? Energy in the car relates back to #2; it doesn't relate to the passengers. Energy in the passengers is primarily managed in a collision. Unless you are talking about a side impact with a disproportionately massive but weak car or a truck carrying a trailer which will move forward and crush the driver.
I disagree with your #4. Greater inertia yes, more difficult to accelerate yes. What about proportionately more frictional force between the ground and tires? This cancels out any effect of greater inertia in the end. You can double a car's mass and expect it to stop in the same distance if all else is held constant (especially center of gravity).

A LARGER car is more safe in all accidents, especially one that's designed to crumple and absorb energy over a greater distance. Mass is only relevant in the "my car is bigger" argument, which yes, there is always someone bigger.

This force you cite here would be important for the tree, brick wall, etc. getting hit, not the driver.
More force acting ***on what object?*** is the specific way to apply this. The increased force acting to stop the more massive car acts *on the car*, and it has more mass, giving it a proportionally equal value of acceleration.
What is experienced by the person inside is relative to the quantity of acceleration they experience inside the car that is having this force imparted to it. Assuming both cars crush say, 0.50m, at the same rate, both drivers experience the exact same force during impact with said stationary object.

*Now if one driver is fatter than the other, HE has more impact energy to be dissipated, and HE will experience a proportionately greater force *acting on him*.

That said I voted for the compact and just drive safely. :thumbup: You can avoid accidents by being observant and alert, and not driving faster than necessary (as you mentioned, velocity is critical in Kinetic Energy)
Most wrecks are due to driver error or inattention so you can save a lot by being careful yourself and watching out for others.

While I agree about absolute braking distances, having driven some big cars that can hang you off the seatbelts under full braking, I have to say: If you double a car's mass, it's not very easy to keep everything else constant.

You can make a very heavy car turn and stop very well, but as Nissan has shown with their R35 GT-R, it takes some really good brake balancing, some really gooey rubber and a really, really stiff suspension to do it. And even then, once the tires give out and physics take ahold of the car, say sayonara... there are some pretty entertaining videos of GT-R drivers running out of talent (or brains) and sliding the car straight into the outside railing.

There was an accident here about two years ago. Local TV celebrity understeered his GT-R off a cliff and killed his publicist, who was sitting in the back seat. Was quite familiar with that road, as I'd driven it just as hard myself a number of times. Wouldn't go so far as to say he wouldn't have gotten into that accident with a lighter car, but I often wonder if he'd have smashed up as hard in something like an EVO, or maybe an Aveo... but given the horrid frontal crash structure of the Aveo,...

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I prefer cars small. Compacts nowadays are bang on the safety ratings of midsized cars, with a smaller fuel economy penalty. Of course, they're starting to get piggishly heavy, but there are those who try to stay closer to the compact norm (Civic, Corolla, Elantra) and are pretty light.

I can swing subcompacts, and I've even driven superminis like the Spark and Hyundai i10 on the highway between semis without fear. At least, not with anymore fear than I would have in the family CR-V.

Except for the fact that tiny cars almost invariably have horrible brakes.

I don't see that in my statement at all. :confused:

Talking about crash avoidance, my answer is still the same. From the list of Camry, Accord, Fit, Yaris and Smart, which will maneuver and get you out of trouble the best? Fit.

OK, I've got a little experiment you can try. Take a pickup (say my '88 Toyota), accelerate to a reasonable speed, and measure your stopping distance. Now put a good load in the bed (say a load of logs for firewood), accelerate to the same speed, and again measure your stopping distance. Bet you find that they aren't the same - 'cause I've tried it :-)

There you go again, with that thing you know for sure that just ain't so. See the actual real world data, as in e.g. the Wenzel & Ross paper I mention.

Which is the main issue with the Smart.
Its structure is very stiff as there's hardly any crumple zone.
As a result, the forces on its passengers are greater.

Well put.

These things could be simple aerodynamic shapes over a well-designed crumple zone.

In addition, all (and all sorts of) vehicles should have their crumple zones in the same height range, so the crumple zones actually crash against each other for maximum effectiveness.

[QUOTE=jamesqf;286788]OK, I've got a little experiment you can try. Take a pickup (say my '88 Toyota), accelerate to a reasonable speed, and measure your stopping distance. Now put a good load in the bed (say a load of logs for firewood), accelerate to the same speed, and again measure your stopping distance. Bet you find that they aren't the same - 'cause I've tried it :-)

QUOTE]

Not always true, I watched a show with 1 ton dually pickups, they stop faster with load, rear tire don't help without some weight back there.

Size advantage is more important when you hit someone smaller in head on collisions, the smaller car will go from 50 mpg east bound to 10 mph west bound (60 mph speed changed spread over the time of crumpling to give the G forces the driver needs to survive) the bigger car goes from 50 to 10, only 40 mph, the crumpling time would be the same, so G forces are way lower.

Turn that big car into semi, car goes 50 east to 45 west, 95 mph worth of G force impact (semi's don't have crumple zone so only one crumple zone, so time is basically half of first first example). Semi goes 50 to 45, on 5 mph impact to the driver as far as G forces go.

Running into a wall all undergo 50-0 decell G force, the longest crumple length reduces the G forces absorbed by the occupants. A longer car would make it more possible to have longer crumple zones, but construction is the key.

The fact that a heavier car has more momentum means it will take longer to stop regardless of what it hits. This means that the impact forces on the occupants will be lower, smoother, and applied over a longer period of time. The impact forces on what it hits are irrelevant.

Weight isn't the only thing that matters in safety just as safety isn't the only thing that matters in a car, however weight is a big determinant factor in safety.

I might add that there are insurance statistics that show a definite trend in an increase in fatalities with a reduction of weight per number of cars registered. In other words being able to stop and turn quicker doesn't overcome the better protection provided by a heavier vehicle

link to follow as soon as I find it.
edit link: not the one I was talking about but the summary pretty much wraps it all up http://www-nrd.nhtsa.dot.gov/Pubs/808570.PDF

...I'm not afraid of "moving" death-traps at all, it's the "suddenly-stopped" ones (with me inside) that I'm afraid of (being in).

After viewing the poll results I am very happy too see most people use common sense. You cannot buy a big and safe car to compensate for a lack of driving skill and awareness. When I am on the road its like I'm behind enemy lines. I don't trust anyone, I am always looking over my shoulder, and I quickly complete my objective and then return home. Any study will show you that the most common cause of accidents is a lack of attention. Now even if you are a great driver its possible to just be in the wrong place at the wrong time and that's just life. But you should not be turned away from compact cars based only on safety ratings. Driving skill and common sense is far superior to having 18 airbags.

I assume you are talking about buying a personal commuter car, not a family car. I would say protecting your loved ones while you are driving is much higher in priorities than mpg. And generally you would need a bigger car for families anyway so shopping for this kind of car sort of takes micros off the table. Buy what you enjoy and feel comfortable driving in. A car that you drive well and know the limits to will be much safer than something you don't like but is considered safe.

That gets back to the issue of design ... a better design will transfer as little energy to the passengers as possible... but the amount of energy the design as to deal with is increased with increased mass... designs have their limits and can only compensate so much for the negative of increased mass.

As I wrote:
It helps but I have my doubts it is a true 100% 1 to 1 relationship.

Tires have limits, brakes have limits, Anti-Lock brakes don't apply braking force 100% of the time, static friction is a function of the normal force not the mass ... on any surface that isn't 100% perfectly perpendicular to gravity the normal force is less , but the interia remains the same... going up hill it might help ... but doing down hill it will hurt... etc.

For example ... my Gen-1 light weight Honda Insight has been rate to stop from 60 to 0 MPH in as little as 120 feet ... which means if the accident is ~120 feet away from when I apply my brakes I have a chance to avoid it completely ... but despite the additional friction from a heavier vehicle from what I see those heavier vehicles always take longer to brake ...
Link
http://blogs.cars.com/photos/uncateg...cetable560.gif
With my 120 feet braking I've avoided the accident that all of these heavier trucks run into.

Not always true.
Double the mass of a car going down a 5% grade ... it has 5% less static static friction for it's tires ... but now has 5% of it's (doubled) weight as an additional force acting against it if it tries to stop.

All accidents?
That is just not correct... in some accidents ... maybe... all ... nope.
The designed to crumple and absorb is a safety technology ... it is what is making such a vehicle safer ... the mass can very well work against you.

If we made that Assumption.

But that assumption does not agree with the example ... because both cars in the example are otherwise equal ... one does not have better crumple zones than the other ... the increased mass at the same speed means they will not both crumple the same ... the heavier vehicle will crumple more ... if it has any crumple zone left to crumple ... if the lighter vehicle had already reached it's crumple zone limit ... the heavier but otherwise equal other car will transfer all the remaining force / energy it still has into the reinforced passengers compartment and those passengers will experience an additional rapid acceleration ... which equals more force to the occupants.

With better crumple zones ... that better safety technology can compensate for the penalties of the additional mass... but even if they do , that doesn't means those mass penalties didn't exist.

Now that I 100% agree with.

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Agree 100%

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Not always.
Once the crumple zone if crumpled the rest of the vehicle is usually designed as a ridged frame ... any remaining vehicle motion at that point is translated into abrupt deceleration.

For vehicles without crumple zones ... like some large trucks ... if it hits a truly stationary object ... it just stops abruptly... with little deceleration.

Also have your vehicle more crushed in an accident is not necessarily always a good thing either... repairable ... or totaled.

Depending on what it hits ... some times it matters what it is that you hit and how hard you hit it.

100% agree... it is not all about weight ... but that is kind of my point ... a lot of people have it in their heads that heavy = safer ... it isn't always true for every situation... does weight matter , yes ... but heavier does not always = safer.

Unfortunately I don't see that link addressing those other issues ... it only looks at reported accidents ... not the non-reported non-accidents because the more agile vehicle was able to avoid the accident or stop sooner ... I've seen other studies make other similar types of comparisons ... but you can't compare against the data you don't have ... ie the accidents that were avoided , and thus never reported.

POINT -- The "safest" accident there is, is the one that YOU are NOT involved in!

well according to this, which is based on deaths per vehicle registered ( which would nullify any arguments that smaller cars have an advantage of avoiding an accident )

http://www.nhtsa.gov/staticfiles/rul...kshop-Lund.pdf

1) (page 13) Occupants of the smallest and/or lightest vehicles still have death rates about twice as high as occupants of the largest and/or heaviest vehicles

2) (page 16) Occupants of heavier vehicles typically will benefit from greater effective momentum

3) (page 17) Smaller vehicles are involved in more crashes (not fewer, as some have hypothesized)

4) (page 24) We will be ok if we let data on what works –not wishful thinking- guide our strategies.

5) graph on page 11 attached