IR reflectivity, you might be able to test with a webcam, but might have to modify it.
I note with my webcams and cheap DVR camera that a red led shows bright white even dimmed, there's so much IR from the led it overloads the sensor. I used webcam to check if my IR's really were lighting when I was having trouble with a circuit, they look white.
With -enough- IR, a cheap webcam might let you check reflection test patches quickly given strong IR lighting and shading the patches from direct room light. If you can see the difference with a webcam, an IR detector should be affected too.
Otherwise:
http://www.wikihow.com/Make-a-Webcam-Into-an-Infrared-Camera
You might try that anyway. You could run the trains in shade or dark with IR spots to make night train movies. (okay, sorry, just could resist)