If street lights were fitted with motion sensors late at night how much electricity would be saved in a year?

Question

My reconning is that the technology must exist to activate lights as needed from a distance... but then doesn't leaving a light on for an hour use less electricity than the act of switching on and off? (Sure I heard something along that theory before but not sure)

Answer 1

Less than you would spend fixing the cars that crashed because the lights don't switch on that fast. Streets light are generally either mercury vapor or sodium lights which produce prolific amounts of light for the power consumed, and when older lights break they are generally replaced with newer technologies.

Both sodium and mercury vapor lights are extremely slow to activate and produce full lighting effects, so switching them off using motion detectors would be a bad move. Switching to a faster light technology would not provide enough light or utilize much more electricity when lit.

If you want to save money try the following:

Remove some street lights, I know that it seems simple, cars bring their own light to the party, and by using headlights rather than external sources that are constantly changing the drivers eye dilation, introducing eye strain, they will have better night vision actually improving safety. Street light should be relegated to security concerns and to highlight road hazards.

Answer 2

It depends on how much people travel through those areas. If there is constantly motion in those places, it would save little or none, but if there wasn't much traffic, then it would save a lot more. I'm not completely sure about the switching on and off thing though.

Answer 3

I think someone did the maths that showed it was more economical to have lit motorways rather than unlit motorways as there were x fewer accidents that cost £y,000 each etc... Not quite comparing like with like but give me a lit motorway ater dark any day.

Ever tried driving on an unlit motorway in the dark in the rain in the US or Germany where they don't have catseyes! Ther'as an invention that has saved thousands of lives, yet many other countries don't have them!

Answer 4

But would`nt that be annoying with all the lights in the street going on and off all night long, I live down a high street

Answer 5

Year they do exist, called PIRs. The lights mostly opperate on light/dark sensors which helps. I would ask why are they not all fitted with a photovoltaic cell (solar panels)?

Answer 6

i can remember years ago if you had a street with 10 street lamps after midnight 5 would go out don't do that any more

Answer 7

I have often wondered this! Surely there must be SOME sort of technology available!