Chennai Trivia - 14

This time I will make it contemporary. Most of us cross the Anna Flyover in Gemini area on regular basis. Right at the apex of the flyover there is a small police shack 2ftx2ftx8ft with a Policeman inside it. Check carefully the next time you go across the fly over. So why is he there?

(I too don't have an answer but only a guess, let's see what you people come up with.)