How does the truvelo speed camera work?

The Truvelo is a forward facing camera that utilises similar technology to the Gatso - By laying virtual loops in the road ahead of the camera, a trigger is used to take a photograph when the speed limit is exceeded or the "virtual" loop is broken.

Picture the camera projecting a set of lines on the road - The time it takes to break the first line before the second line is broken determines whether the speed limit is being broken.