I've had a few emails with Bryan Walker from the City of Madison (Wisconsin) Transportation Department about their attempts to use portable, pneumatic hose counters to count bicycles on trails. Click on the graph to see the results of their latest test (buried inductive loop vs. old ADR Hose Counter vs. new MetroCount brand Hose Counter).
Here's a portion of the email from Bryan –
"In our first trial,
we used a very heavy duty brand tape (brand: Polyken) which may have
the compression of the hoses and caused lower counts. In this last
we used the Gorilla brand tape that you recommended and the results were
better. We used the mini tubes for both trials, as I was unaware that
had used the mini tubes for the first trial. I can’t yet explain why
older ADR’s seemed to have double counted all the bikes, but using a
different report set ups, the MetroCount seemed to be reasonably close
buried loop. One possible cause of the buried loop being off is the
different types of metals used for bicycles may have different effects
loops picking up the magnetic waves. I’m looking at doing a manual
next to the MetroCount as the next possible test."