Predict the number of red lights in Delhi?

Number of red lights refers to the traffic signals on the roads of Delhi, not any other lights which are red in colour!

We know that Delhi is approximately 1600 sq.km in area. This is pretty much evenly divided between North, South, East and West. Imagine Delhi to be a square area with dimensions 40*40 as length and breadth. We divide the entire city into blocks of equal area, hence, 20 blocks from east to West and 20 blocks from North to South (with each block representing 2 sq. km) Every intersection of four adjacent blocks would give us a cross road. Each crossroad would have a traffic signal. Hence, the number of signals at crossroads would be 400 across Delhi, averaging out for different areas.

Since there are 400 crossroads in Delhi, the number of red light at each crossroad is 4.

Hence, the total number of red lights at crossroads in Delhi is 1600

Let us assume that there are 20% additional red lights to the ones found at crossroads that are meant to control traffic on straight roads. These would amount to ~300 red lights.

Thus final Ans = 1600+300