this post was submitted on 28 Apr 2024
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What is this thing?
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What I'm saying is they use a double to differentiate counts between passenger cars and semi-trucks (aka tractor trailers, 18 wheelers). Sometimes you want a count of 1) passenger cars and 2) semi-trucks. That's what I remember learning it was for. I'll edit my previous reply in case people are misreading it.
You can do that with a single line. It's a closed, flexible tube with a pressure sensor. Effectively a crude scale. It measures the weight on the axle. Semi trucks weigh a LOT more than passenger vehicles, even ridiculous pickups.