In a village near me there is a lamp-post in a 30 mph zone which has a rectangular metal "tube" about 1 foot long by 6" square which is pointing straight down at the road surface by the post. There is also another device alongside, again pointing at the road. There are no road markings like you get with speed cameras. I presume the larger device is a camera and the smaller one is a light. The cameras are angled so steeply that they could not see the number-plate of a car. There is also a box on the lamp-post which may be some form of control module.
Any ideas? I'm intrigued.