I have an Illinois Pass, which just sits in the glove box.
During a road trip back in 2011, I went from Illinois, to west coast, then east coast and back. While I was in NY, had to go through a tollway and was about to pay… but the guy there said it was already paid. Ever see comics where a person suddenly has a bunch of ?’s around their head? That was me at that moment. Initially I thought the guy in the car in front paid for some reason. But the guy in the booth said it was a pass device that had to be in my car.
So I learnt two things right there… Illinois and NY use the same system (specifically, I can use ipass anywhere where EZPass is used) and the ipass works from the glove box. Ever since then, I left it in the upper glove box.
When I got the HR-V, I got a second ipass tested to see if it would still work in the (only) normal glovebox and it did.
Checked again when I got the MYP (the same ipass from the traded HR-V)… still works, though I don’t go through tollways all that often. But had to go through tollways to get to airport when family visited.
On the complete flip side, my sister and brother-in-law found out that they can’t have the ipass anywhere inside of their BMW, it just won’t work even on the windshield, so they had to get one that mounts onto the license plate.