Chennai Trafiic Light - Power Cut - Solar power

Today, when I was reading Dinamalar newspaper, I have noticed one photo. It sis showing the traffic jam and was depicted as due to power cut.

Are those traffic signals are depending on main power supply of the city?
If so, how come no actions are taken to provide uninterrupted power supply till now, or after the power deficiency started in Chennai.
Why can't we install mini solar system to produce required power to function the system without any interrupt?
Why there is no power battery backup system installed to avoid the system failure due to main power supply cut?