Miata Mailing List: July 1993, Message #131
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   From: buck@granite.ma30.bull.com (Kenneth J. Buck)
Subject: Rollbars & rollovers
   Date: Thu, 15 Jul 1993 08:25:12 -0400


someone asked about rollbars recently, so i thought i'd also
post part of my reply to the list for general entertainment.

> Any specific info you could provide would be great; even the date of the
> article would be very helpful.

a bunch of roll bars were reviewed in the Fall 1992 Miata Magazine.
back issues s/b available, but if necessary, i can extract details from
the article for you.

(for those of you who aren't members, the address is:
Miata Club of America
P.O. Box 759
Lilburn, GA  30226

dues: $25/year US, $35/year Foreign)

as for the roll bars reviewed, some are simple hoops (probably can't
count on these for much protection), some are hoops with an angled brace
(better, shouldn't fold over). some attach so you can use your soft top,
others don't.  nobody warrants anything as providing actual protection
(too many lawsuit possibilities) but it's pretty obvious that some
ought to help more than others.


for some numbers to quantify the risks, the article says (summarized):
based on NHTSA figures, about 4% of the 150 million cars in the USA
are involved in accidents each year, 2% of which involve rollovers,
and 7% of the rollovers involve fatalites.  rollover data is skewed
by a large number of SUVs, which tend to roll more easily.

assuming the data are correct,
(a) your chances of being involved in an accident are .04 (1 in 25),
(b) your chances of being involved in a rollover are (.04)*(.02) = .0008
(1 in 1250),
(c) and your chances of getting killed in a rollover are
(.0008)*(.07) = .000056 (1 in 17,800).
since we drives Miatas, not SUVs, our actual chances are probably somewhat
better than this.  other contributing factors include how old you are,
how crazy you drive, whether you drink, where you drive, and how much
you drive.

those percentages sound pretty good, but on the other hand, the raw
numbers don't sound quite as nice.
(.0008) * 150,000,000 = 120,000 rollovers per year
(.000056) * 150,000,000 = 8400 rollover deaths per year
i'd really rather not be in either of those 2 categories...

--

something else to consider is that over time, the odds multiply.
so over a period of 10 years of driving, the chances of getting:
(a) involved in accident: 10 * .04 = .40 (2 in 5)
(b) involved in rollover: 10 * .0008  = .008 (1 in 125)
(c) killed in rollover:   10 * .000056 = .00056 (1 in 1785)
something to think about.


personally, i think the risks are low enough for me, given the
type of driving i do, that it's not a big deal.  it's a decision
you have to make for yourself.  for those that don't agree, i guess
that's why there are companies that sell roll bars...