[MrUnknown]

Usually detecting them can be too late. They can clock your speed and take your picture extremely fast and work in a very focused area usually.

The detector would have to catch "Scatter" from it from cars going through it or whatever. Which, IR is emitted from many sources, so it couldn't be used as a reliable way to detect it.

Also, a lot of the triggers are by video cameras. If you have ever setup any basic home security system(Like Q-See), you can choose areas as "Triggers" for recording. The operators of the cameras basically draw out areas that act as trigger zones. See this as something of an example: http://rhythmtraffic.com/wp-content/uploads/2012/10/WebUI.jp...