In our homes, the budget-minded among us will turn a light off when leaving a room. There's no point in paying for electricity when no one is around to reap its benefits. But this money-saving tactic has traditionally not been possible with highway lights, which municipalities are obligated to leave on all night in case a car should pass.
The Norwegian municipality of Nes I Hole has therefore installed sensors on their light poles along their local Highway 155. With no cars around, the lights default down to 20% of their power; as soon as they detect an oncoming vehicle, the lights kick up to 100%, and communicate with each other to synchronize the illumination with the car's presence. Here's how it works:
As stated in the video, the system will pay for itself in under five years, and other countries with higher energy costs would reap the savings even faster.