From: miller@FS1.cam.nist.gov (Bruce R. Miller)
Newsgroups: alt.autos.antique
Subject: Re: Old Car Emissions (Update)
Date: 9 Oct 92 23:39:41 GMT
Organization: NIST - Computing and Applied Mathematics Laboratory


In article <1992Oct5.215116.14261@newsgate.sps.mot.com>, Mark Shaw writes:
>  (Bruce R. Miller) writes:
> |> WHOA!! That's what you call paraphrasing??? ...
> |> Someone classified type-b dogs and claimed, to the effect, that noone
> |> would miss them.  I just wanted to make the point that there are poor
> |> people who use & need these for transportation and have _NO_ chance of
> |> buying a new car, clean or not. 
> |> Other than ephemeral things like "heritage" and Hobbies, _THESE_ are the
> |> people that would be hurt most by any plan to smash old cars.
> 
> Sorry Bruce, this "politically correct" concept of saving old cars for
> the poor to use is a real hot button for me.   If we are truly concerned
> with the welfare of the poor, we would find a way to get them reasonable
> transportation.  I sure that this topic is not a part of alt.auto.antique
> charter, so I don't think we should use it as a defense for something that
> also helps us.   Our arguments for saving old cars should stand on their own.
> I didn't mean to condemn you for making the comment, I just spiced it up
> a bit to get the point across :-)

I'm pissed off with your gross distortions of what I said.  This is
the second time.  Frankly, it makes it quite difficult for me to
convince myself that the other distortions of the data you made were
unintentional.  

In any case, please quit pushing your own hot button in public.

> ...
> The 1974 data is an estimate by the EPA to correct for the variations
> in test methods.  The pre-68 data is an estimate by the MVMA.  It is
> interesting to note that their estimate is more pessimistic than mine.

"Interesting" ?!?! That's what I was telling you in the first place,
but you wouldn't hear of it.
..
> So taking my more optimistic ratios of 13:1 and 8:1 and looking at
> number of old vehicles reported by R.L.Polk and compiled by MVMA:
> 
> Total Number of vehicles in use 1990:      123,276,000      100.0%
> Vehicles in use 1990, built 1982-1990:      79,157,000       64.2%
> Vehicles in use 1990, built 1976-1981:      32,399,000       26.3%
> Vehicles in use 1990, built before 1976:    11,720,000        9.5%         
>
> If we make the really simple assumption that these cars all drive
> similar missions (miles to/from work) and that anything pre-1982
> is 8 times worse that post-1981 then there are 35.8% of the vehicles
> puting out 8x:

Considering the poor resolution of the data given, we have to make some
simple assumptions to extract some information, but this is ridiculous.
  1) There is a somewhat steep distribution of the cars across the
years: for example, for  the period 1976-1981, there are many more 81
models than 76 models.  Furthermore, those 81 models polute less than
the 76 models.  
  2) The assumption that "all drive similar missions" is patently
absurd.  Sure, the guy down the street put 20Kmiles on his model T last
year.  Probably half those pre-1976 aren't even driven!

> 
> 64.2 x 1 =  64.2
> 35.8 x 8 = 286.4  82% of total!
> 
> Pretty gross, huh?  

Not all that much.  So 36% of the cars produce 82% of the pollution.
Yep it's disproportionate, but get real.
What's gross is the distortion.  

Let's try this differently. Make the number-of-cars/year a piecewise
linear function (you still have to guess abit, because the figure in the
table are too coarse).  Do the same with the pollution figure.
Now you can sum up the product per year over any range you want.
Now you get a figure more like 36% producing 74% of the pollution.
Still not great, but not as bad.  

Oh, I notice that suddenly "older cars" is defined to be 9 year old or
older. If you adjust that to 10 years or older, the figures shift to 30%
producing 69% of the pollution.  Hmm, still less dramatic.

Here's another interesting effect, if you assumed the same distribution
of car ages 10 years from now, with the improved emissions and
attrition, that 30%  produce only 42% of the pollution.

And of course, if you would correct for the differences in car use,
it would come down even further.   Gee whiz, what happened to all the
drama.

Now we can discuss the lower mileage use of the
> older cars, but they would have to be used on average about 1/4
> as much as new cars to still account for 50% of pollution.

That wouldn't surprise me a bit.
> 
> Spooky numbers, I agree.   The real numbers that shock me are the
> large number of older cars.  In 1970 there were only 6.2% of the
> cars were more than 11 years old.  By 1990 that percentage jumped
> to 20.3% were more than 11 years old.  People are just keeping
> their cars longer (both rich and poor alike).
> 
> Mark

It just seems curious that every assumption you make  has the effect of
inflating the emissions of older cars.
I think the issue is a straw man.
Newsgroups: alt.autos.antique