On Wed, 10 Aug 2016 18:28:15 +0100, wrote:

On Wed, 10 Aug 2016 16:08:08 +0100, "James Wilkinson"
wrote:

On Wed, 10 Aug 2016 14:11:43 +0100, Pat wrote:

On Wed, 10 Aug 2016 03:09:05 -0400, wrote:

I've always wondered how they work, and
why they dont detect cars going the opposite direction.(I assume they
work on radar). ???

Yes, they work on radar. Cars going the opposite direction DO get
detected, but they show up as going a negative speed. The built-in
software just ignores those signals and displays only positive speeds.

If it's aimed along this side of the road, it shouldn't see cars on the other side.
Otherwise what happens if there's cars going both ways at once?

If there are a line of cars approaching the sign, the numbers tend to
jump around quite a bit. So which car is it sensing? (Of course a line
of cars are all doing roughly the same speed).

How much does it jump about? I could believe a line of cars varying by something like 28mph to 34mph.

--
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