• Mar 12, 2008
There's been considerable debate between automakers, legislators and safety advocates over how roof strength correlates to deaths in rollover crashes. The majority of the focus has appropriately been heaped on SUVs, whose high center of gravity makes them more prone to rollovers, particularly when they leave the road.

The Insurance Institute for Highway Safety has just released a study that proves that more roof strength can reduce injuries by some 39 to 57 percent when compared to the weaker models it tested. The IIHS used the same roof strength test as the feds on a group of SUVs that currently meet the government's roof requirements. At the top of the heap was the 2000-2004 Nissan Xterra that was able to withstand almost 12,000 pounds of force, while the lowest ranked vehicle, the 1999-2004 Jeep Grand Cherokee, lost its head(room) after 6,500 pounds of force was applied to the roof.


[Source: IIHS]


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  • 25 Comments
      • 6 Years Ago
      There shouldn't really be a question as to whether stronger vehicles are safter; the question is if we need to do anything about it. Sure making a roof twice as strong will help prevent it from caving in, but it will also add weight, which removes performance requiring upgrades everywhere in a car to regain its former agility and handling, and all of that weight means you need a stronger roof again. In this article they are implying that we have to make cars safer.

      Cars already weight 4,000+ pounds; let’s not keep up this bad design. Light cars use less fuel to do the same thing and are easier on the roads. Are 10, 100, 1000 people a year worth a penalty on everyone else?
      • 6 Years Ago
      The tests are interesting, the stupid "duh" marketing aspect of the report is stupid. Of course a stronger roof is going to be better in a rollover.
      • 6 Years Ago
      Remove all safety requirements. Test vehicles and require crash results to be posted on the window sticker. Let the public decide how much safety is enough.

      Right now our only choices are an armored steel cage with an average weight probably over 4000# or a motorcycle. Please, I want something in between. I am willing to trade some crash safety for reduced weight and increased accident avoidance ability but I do not want to go as far as a motorcycle.
      • 6 Years Ago
      Why is this a GM and Ford problem?

      Read the article and you'd find that the '02-'04 Explorer had a HIGHER rating at 10" compression than the XTerra, and the '96-'00 Toyota 4-Runner had a LOWER 2" crush rating than the earlier Explorer.

      And no automaker will be free of this standard with an all-electric car. That weight will still impact your range in the city to some degree, much like it impacts fuel economy.
        • 6 Years Ago
        Above was aimed at Nacon...
      • 6 Years Ago
      Yes, we all know that stronger roofs are likely to save more lives. Duh!

      The point of the study is to quantify the potential number of lives saved, only then can an economic analysis be done to determine if it's worth it. Yeah, I know, someone will say a life is worth more than money, or some such nonsense, like you can't trade a life for money. You know what, you do it all the time without thinking.

      Let's say you mandate a SWR of 3.16 and save 212 lives, as predicted. What if it costs $10 car, would you pay it? You would? Let's see, if there are 10 million cars sold in the US each year, adding $10 each would mean $100 million extra in costs, while saving 212 lives, or $470k per life. That's a good tradeoff, as the US Govt has calculated the loss of one life is worth more than $2M each.

      However, if it cost $100 to require each and every new car have a roof able to withstand a SWR of 3.16, that would mean spending about $1B in additional mfring costs to save 212 lives, which comes out to $4.7M per life. You may think that's a good tradeoff, but there may be better ways to save lives, that are in fact, cheaper.

      Let's say hypothetically, studies may show that improper inflation of tires leads to rollovers and subsequent death in SUVs. Perhaps, requiring air sensors in SUVs would lead to fewer rollovers and fewer deaths, just like requiring stronger roofs, and at a lower cost.

      That's just an example of why these safety issues are complicated, and not such a simple thing to mandate. Not to mention that strengthening roofs raises the weight high up in an SUV, which raises the center of gravity, COG, which makes rollover more likely. Unintended consequences, you got to think about them.
      • 6 Years Ago
      This doesn't answer any questions.

      Yeah, stronger roofs are tougher to crush. Do they lead to safer vehicles is the question. Making stronger roofs will lead to putting more metal up high in the vehicle, which will lead to higher center of gravity and more rollovers.

      A good study would tell us whether adding weight up top helps or hurts overall safety.
      • 6 Years Ago
        • 6 Years Ago
        Makes me even more glad that my wife drives an Outback (now when will the diesel be here...?!)
      • 6 Years Ago
      I'm surprised this was even a debate.
        • 6 Years Ago
        @ Kaptain,

        Umm... IIHS isn't a government agency. This study came out of insurance premiums, instead of tax dollars.
      • 6 Years Ago
      Nice to see the lowly Nissan Xtera get a little respect.
        • 6 Years Ago
        Although I've never had a need for an SUV, I've always liked those Xteras. Glad to know their ruggedness isn't just painted on.
      • 6 Years Ago
      I wonder if the unique two-tiered shape of the Xterra's roof has anything to do with it's outstanding performance?
      • 6 Years Ago
      What's really odd is that insurance companies charge more if you have a roll bar in a convertible - your odds of survival without said roll bar are zero.

      Perhaps the IIHS calculated that it was cheaper to pay out life insurance than hospital bills for head & spinal trauma.

      • 6 Years Ago
      Please, by all means. Make vehicles safer.
      Make the roof bars stronger.
      However, as vehicles are so frikkin heavy now, use lighter materials.
        • 6 Years Ago
        Problem is, lighter materials are also more expensive materials (high-strength steel, aluminum, carbon fiber).

        And per the studies' own conclusions, "108 of these lives (95 percent confidence interval: 63-148) could have been saved by increasing the minimum SWR required by FMVSS 216 from 1.5 to 2.5. Increasing the minimum SWR to 3.16 could have saved 212 lives (95 percent confidence interval: 130-282)" [IIHS document r1098.pdf, page 11]. Now if we expanded this to the whole country, we'd still be talking about relatively small numbers... perhaps a thousand or so vs. the 43,000 that die a year in the US.

        That number isn't small, but begs the question: how much do we spend to save a life?
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