LED streetlight over a sliproad by the A9, in Inverness. Some of the older lights have been replaced with these very slim LED types. The slight fins on top are to keep the LED's (light emitting diodes) cool. And the thing on top is for monitoring and controlling the light - all the ones replaced seem to have these.
Some advantages of the LED types include: using less power; more natural light colour output; longevity; reliability; instant turn on to full brightness; not bothered by frequent turning on and off; and they can be dimmed, for more power saving. They were much more expensive at initial introduction, but that's no longer the case, as more and more of them are introduced, and used. The performance of newer types keeps improving too. Be wary of looking straight at the lights, as they can be very dazzling.
The technology's much better than when one of the Students was playing about with a couple of them for a project a few years back. He'd just two of them for his light. Modern ones, like above, have an array with many of them, normally arranged in a grid.
Was going to add a photo of it switched on tonight, with near horizontal rain passing through the beam... but getting home pronto was a higher priority!
(Taken from the "Golden Bridge".)