>
>
> Second, try NVE's line of giant magnetoresistive sensors.  The most
> sensitive
> ones can detect a screwdriver a foot away; I think they'd have NO trouble
> with
> a car, even up to a couple of meters.  They're also cheap.



A large diameter coil, and current-voltage amp will detect cars quite a ways
away.
In hawaii, I expeimented with this using a six inch coil of a few turns, and
was able to see traffic on the street three floors down and about 20 feet
away.
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