Does Bigger Mean Safer?
Tuesday, February 16, 2010 at 02:18PMThe Very Light Car is designed to be a highly efficient, very safe car. But an assumption many people make is that a small, lighter car is less safe and that a big, heavy SUV is more safe.
Wrong. In a 2004 New Yorker article Malcolm Gladwell completely demolishes, so to speak, this assumption. In Big and Bad: How the SUV ran over automobile safety he shows that while an SUV may be safer if you run head-on into something (“passive safety”), the problem is the trouble a heavy vehicle has in accident avoidance (“active safety”), ie, swerving and stopping. As he says, “The benefits of being nimble – of being in an automobile that’s capable of staying out of trouble – are in many cases greater than the benefits of being big.”
This concept is backed up by research: in An Analysis of Traffic Deaths by Vehicle Type and Model scientists from Michigan and Berkeley conclude “…utility vehicles (SUVs) are not necessarily safer for their drivers than cars; on average they are as risky as the average midsize or large car, and no safer than many of the most popular compact and subcompact models” and that “when one considers the combined risk, including those killed in the other vehicle in two-vehicle crashes, then the safest subcompact and compact models are actually safer than the average SUV”.
Perhaps the most interesting concept in Big and Bad is the importance of an awareness of your surroundings – and your own vulnerability – that comes with a small or normal-sized car, compared with the feeling of invulnerability an SUV conveys: “Jettas are safe because they make their drivers feel unsafe. S.U.V.s are unsafe because they make their drivers feel safe. That feeling of safety isn’t the solution; it’s the problem.”
Reader Comments (3)
I appreciate your forum as a way to discuss the automotive issues. You make very good points. However, there are further things to say.
As you say, bigger does not necessarily mean safer. Accident avoidance is a significant factor. However, "big" does provide a degree of safety in the structure that surrounds the people. There is also a benefit that "big" means the change in momentum will be less for a head-on collision situation. It also means that there is more room for crumple space ahead and to the side of the passengers.
Very impressive things have been done with composites, so there is much to be hoped for here, however, the often unrecognized nature of composites is how they shatter in the failure process. Here we have sailboat experience to draw on, where all the great features of composites have been well utilized; however, where boats hit rocks, most experience shows the ability of steel to deform and still retain much of its integrity should not be taken 'lightly'.
Marketing issues are relevant here as well. As engineers we like to believe that technical reality is the basis of decisions. Unfortunately the public perception of safety is something that has to be recognized. Here the "big" wins quite easily. Accidents like the one where a Tesla rear-ended a Mercedes does not help in sales. It looked like the Tesla had tried to crawl under the Mercedes and was seriously squashed as a result. The Mercedes was slightly lifted, and that was about all the damage it suffered. I think Tesla has done a good job with structure, but appearances really count.
The Tesla stuck with its nose under the Mercedes brings up another marketing issue, which is that the "puny" factor has been a cause of failure of many historic automobiles, which otherwise seem to have had a lot of merit. The names Isetta, Messerschmitt, and TriHawk should bring up images of significant past achievements, which did not prevail in the market, even though some very big corporate forces were behind them. I believe BMW backed the Isetta, Harley Davidson bought Tri-Hawk, and Messerschmitt had its own deep German pockets, just to put some sobering reality on the subject.
A similar, but slightly different issue is the vantage point of the driver. Those of us who drive around in low cars know very well how annoying it is to be unable to see over the hoods of most other cars; not to mention the less than beautiful view looking into wheel wells and the under-side of trucks. I recall once being told by a pickup owner how much he liked being able to see over traffic.
My last point is that you folks at Edison2 seem to have bought a hazard that limits accident avoidability, as well as creates a significant hazard in itself. This would be the wide set wheel system. A similar problem would seem to be troubling the Aptera folks, so much so that they have yet to publish an overall width dimension.
So with these thoughts in mind, perhaps the reason for the design choices that led to the Miastrada concept might seem sensible. Light weight was important in the design trade-offs, but not to the exclusion of other concerns. Fine tuning of that weight is yet to be completed. The Miastrada car would also not be so restricted to internal combustion engine, since the flexibility of electrical devices can make safety enhancing arrangements very attractive.
Jim is a guy who wanted to compete in AXP with driving amphibia on six wheels, but couldn't. He didn't pass the first stage of selection. So now he's posting info about his on-paper Miastrada on every blog and website about cars and green issues on this planet. It's getting boring Jim to see you once again selling your rejected ideas. If you could build a car you would do it long time ago.
Hi Matt,
Buck up buddy. More is still to come. I try to write stuff that will be useful to others as well as raise interest in my approach, but feel free to skip over reading my comments.
I am aware that real innovation is hard to sell.
A one person operation might be expected to build a car step by step. Yes, the first steps are on paper.