Mother Talkers

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  • Well, it does matter (0 / 0)

    Because a 70 MPH crash is obviously a totally different kettle o'fish from a 35 MPH crash. The legal standard is 30MPH.

    The reason that it's considered "ok" to test at those lower speeds is that there's an assumption that the drivers will brake before impact, just not stop in time. So it's rare to actually collide at 70mph - usually, you'd see the obstacle, brake as hard as you could, and collide at a slower speed.

    That's the rationale. It's also a matter of practicality, in that it's considered achievable to protect the occupants at that speed while maintaining appropriate cost and fuel efficiency and passenger comfort and other concerns. Just as buildings are designed to survive hurricanes or earthquakes or fires of a given severity that is usually less than is theoretically possible.

    However, in a head on collision, you have to add the speeds. So if both of you slow to 35 MPH, that's the same as hitting a fixed barrier at 70 MPH.

    by shenanigans on Fri Jan 19, 2007 at 11:35:44 AM PDT

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    • If it makes a difference (0 / 0)

      The tests were side-impact, so the multiplication of force would probably work a little differently than a head-on collision. Though I'm not sure how--I barely made it through high school physics.

      The issue with the seats is they were coming off their moorings. If an object hit the side of my vehicle at 70 mph, I wonder if that would function more like an emergency-eject feature?

      by minnmom on Fri Jan 19, 2007 at 11:54:19 AM PDT

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    • Side-impact (0 / 0)

      Do those side-impact air curtains they have now help with kids in the back seat?

      by NJmom on Fri Jan 19, 2007 at 12:29:14 PM PDT

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    • I'm not sure about the head on collisions -- (0 / 0)

      A true head on collision with two vehicles going 35 mph would equal 70mph of force.  But in most head on collisions the crash is off set a bit -- picture two front corners of the car colliding.

      From what I was reading it puts lots of stress on just one part of the car but doesn't necessarily equal 70mph of force.

      Anyone a physicist around here???  (Not me!)

      by Anu on Fri Jan 19, 2007 at 01:56:07 PM PDT

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      • Well, I have a degree in Mechanical Engineering (0 / 0)

        You're right - in the real world cars never hit dead on and square. But there's no way to test every possible combination. The off-set crashes are a very good addition to the suite.

        The offset crashes are much more severe than the head on, because there's less vehicle to absorb the impact of all that mass coming to an immediate stop behind it.

        Another variable is if the cars are different sizes and different structures. Passenger cars are designed to crumple around a strong passenger compartment, sacrificing the engine and frame to protect the occupants.

        Here I'll add in a particular peeve of mine: people assume that heavier vehicles are safer, but SUVs and trucks don't have to meet the same safety standards as ordinary cars, and don't crumple as well. Those vehicles, for example, are very likely to roll over or to be in solo vehicle accidents, where being big and heavy is no advantage. Rollovers are 14% of accidents but over 50% of fatal accidents.

        by shenanigans on Fri Jan 19, 2007 at 02:19:27 PM PDT

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        • Love our car for its safety profile (0 / 0)

          We have Subaru Outback with electronic stability control.  For cars with a higher ground clearance (which we wanted to drive on Forest Service roads) this car wins for safety.

          Electronic stability control is supposed to really reduce rollover risk -- especially in cars/SUVs with a higher center of gravity.

          by Anu on Sat Jan 20, 2007 at 11:59:14 AM PDT

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          • Hee, another Outback fan here! (0 / 0)

            I still love it even though it is thoroughly coated with dog hair and child goo after all these years.

            I took it in to be detailed when it was about 5 years old. The guy looked at it and said, "Um, lady, I'm sorry, but I'm going to have to charge a little extra for this." But when I picked it up, he added, "You know, I don't see many of these, but when I do, they're always filthy, the kind of filthy that you get from going a lot of fun and interesting places." :-)

            by shenanigans on Sat Jan 20, 2007 at 04:38:19 PM PDT

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