>>A 2 foot by 3 foot barcode should be readable from several feet, no?
>
>Railways use these. Readable from a  distance

I thought the US railways had tried these and given them up, as the dirt
needed to be washed off on a very regular basis to get reliable reading.
Maybe they have improved the reader technology to where the dirt is less of
an issue, I know there is optical recognition technology that can read
number plates despite great mud splats on them. I believe Australia uses
this type of technology to try and keep truckers speeds and hours down.

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