If the Infrared's are lit, those are the ones that work. If you stare at them when you pass, you see the glow of the bulbs. (Obviously i'm talking about in the dark)
Can these infrared cameras see the number plate even with the headlamps on, after all they emit a lot of infrared along with the radiator all of which are only inches away from the plate? Wouldn't all of this in effect blind the camera just like taking a photo of someone with the sun just over their shoulder can result in there being no detail in the face?