The first right way of using a hidden sensor

Screen shot 2014-09-19 at 5.52.43

My usual cycling route become under construction and a pair of temporary traffic lights were installed at both ends of the construction sight in order to control traffic going on one side of the road.

I then noticed those traffic lights were unusually smooth. Observing them carefully, I found these black devices on top of them! They are sensors and switch the lights to green right away when nobody is on the other side.

It seems the first right way of publicly using hidden sensors, before, they were only used for horrible security home outdoor lights. They have been annoying me everywhere.