Have you ever seen the city lights at night ... noise pollution right? Well what about all the costs associated with those lights? Think of all those huge parking lots that have giant lights glowing all night long ... why? Now the facility owners and management will tell you it's about security, which is vaguely reasonable. However, they only need to be on when someone is there.
IDEA: Add motion sensors to all those light poles so that when someone moves in the area at night, the lights come on, but otherwise it is peacefully dark and quiet. Given the spacing of these poles typically should create a "grid" that would light an area with any activity - security maintained. Plus the cost savings from electrical conservation.
Reward: Credit for expressing the idea.