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4312Re: More pollution from slower traffic

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  • turpin
    Feb 6, 2002
      --- In carfree_cities@y..., Mark Jaroski <mark@g...> wrote:
      > Frankly, it's simply not true at all. Yes, an engine
      > has an optimum running speed, but it's measured in rpm
      > (rotations per minute) *NOT* km/h.

      You're half-right. Yes, engines have an optimum RPM, FOR
      A FIXED LOAD. But the load depends on the speed and the
      car. That doesn't answer the question of how to make a
      trip in an automobile with minimum pollution. And if you
      ask THAT QUESTION, then it depends on the car as well as
      the engine. And for most cars, the answer is that you
      achieve minimum pollution per mile by driving at a steady
      rate, near highway speeds. The "steady rate" is the more
      important part of the answer. A car driven at a constant
      30 mph will use less gas and pollute less than one driven
      stop-and-go, though sometimes up to higher speeds. In
      fact, stop-and-go driving has a lot of harmful effects,
      not only in pollution, but also in wear and tear on the
      car, increase in accidents, etc.

      Now: there's always the issue of how important that
      fact is in relation to the variety of concerns at hand.
      But please, don't deny a fact just because it's
      inconvenient. It only hurts your credibility when you
      raise those other concerns.
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