Countermeasures to radar speed traps?

[Barry Gold]

I've thought of what looks like a simple countermeasure to radar speed
traps, and I'm wondering if it would work.

You mount a corner reflector on the hood of the car and spin it.
Radar guns and cameras are, IIRC, designed to pick the reflection from
the fastest-moving and largest target (in that order of priority).

Now, the bounce back from the corner reflector is much stronger than
from your car. To an approximation, the reflection from the corner
reflector decreases as inverse square, while the reflection from your
car (effectively scatter) decreases as inverse fourth power.

So the corner reflector should look "bigger" than your car to a radar
receiver. If it's spinning so it looks like it's moving at 120 mph or
so, it should produce a reading that will convince a judge that
there's "something wrong" with the radar machine. "But your honor, my
old clunker can't possibly go that fast."

(Heck, I don't think my Mazda 6, which is pretty hot, will go that
fast -- even when brand new. Not that I've ever had it over 80, and
that on rural parts of I-10.)
--
Barry Gold, webmaster for:
Conchord: http://www.conchord.org
Los Angeles Science Fantasy Society: http://www.lasfsinc.org
My blog: http://goldslaw.livejournal.com/

[ji...@specsol.spam.sux.com]

Barry Gold <bg...@nyx.net> wrote:
> I've thought of what looks like a simple countermeasure to radar speed
> traps, and I'm wondering if it would work.
>
> You mount a corner reflector on the hood of the car and spin it.
> Radar guns and cameras are, IIRC, designed to pick the reflection from
> the fastest-moving and largest target (in that order of priority).
>
> Now, the bounce back from the corner reflector is much stronger than
> from your car. To an approximation, the reflection from the corner
> reflector decreases as inverse square, while the reflection from your
> car (effectively scatter) decreases as inverse fourth power.
>
> So the corner reflector should look "bigger" than your car to a radar
> receiver. If it's spinning so it looks like it's moving at 120 mph or
> so, it should produce a reading that will convince a judge that
> there's "something wrong" with the radar machine. "But your honor, my
> old clunker can't possibly go that fast."
>
> (Heck, I don't think my Mazda 6, which is pretty hot, will go that
> fast -- even when brand new. Not that I've ever had it over 80, and
> that on rural parts of I-10.)

Radar guns aren't smart, the beam width is rather narrow, and the vehicle
speed they read is the speed of the vehicle the cop is looking at through
the radar gun sight.

If the gun indicated a "funny" speed, the cop would just aim at a different
part of your car.

--
Jim Pennino

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