Recycling comment from another submission 17 day ago:

Random thought: If you stick a very small adhesive mirror to the outside window before boarding, then footage "looking down" at the regularly-spaced railroad ties could contribute to information about the current speed and acceleration.

Well, on a straight section anyway, if you turn, the inner/outer edges will appear differently-spaced...

Wouldn't do anything positive in terms of suspicious staff though. They might think it's like some kind of heist-movie that will involve a specialized glass cutter making a circle on the window.