Current streetlights (sodium lamps, anyway) aren't on motion sensors primarily because they have a relatively long warm-up time between switch-on and full luminance. This means that all of the lights would need to communicate with each other so that they could light up sufficiently in advance of your arrival.

Even groovier idea: your car logs the route from your navigation system into a national database (ignoring for a moment that this means the government knows your every move), and if you're the only person on the road, then only your route is illuminated, and only when you're going through it.

I think this is more appropriate for lesser traveled roads and perhaps we need new bulb technology to support it.Obviously major emergency vehicle routes would need 24 hour service.

Certainly motion detectors can tell if anyone is out "needing" those lights... and certainly CARS don't need streetlights.... i thought the whole idea was it theoretically reduced street crime... ha!

This idea is excellent. On flying from New York to San Francisco, the ground below is lit a good portion of the way across the country... and surely the need to light several thousand miles of open space is not anything but wasteful.

Um, what about the people walking home in the pitch black at 1am? You'd be pretty much enforcing a curfue for many people.

As for motion sensors - that would just end up with flashing streetlights instead of constant ones!

And turning those kind of lights on and off wastes more electricity than just leaving them on does.

I live in the UK and certain local authorities are already installing directed lighting, which I understand uses less power and ensures the light doesn't seep into the sky. There are also schemes, particularly in villages that use motion sensors and dimmer technology to turn the light up as someone walks past and dim it again when they have passed.

The idea that cars don't need street lights is an interesting one. Having lived in countries where sometimes there isn't any street lights I can say from experience it is a lot more hard work driving in such conditions if there is a lot of traffic, vehicular and pedestrian.

On a trip to the Ukraine in non-tourist season, the smaller cities actually disconnected their lights, and the local drivers were used to it. Now, this was actually due to the fact that they couldn't pay their bills, but still, the concept of not having the lights on when not needed is a good one.

The sad thing is the implied safety liability, once a light has been installed, and there is a reasonable expectation that the light will provide a safer environment. If a city did anything to turn off some of its lights at night, and one "thing" happened ( a pedestrian or car accident, an attack on someone, crime incident, whatever), there would be a field day of lawyers, lawsuits, and publicity.

If people can sue and win $$ for spilling hot coffee which is completely under their control, they would also win a lawsuit in this case. And I do not think any city would float a referendum to turn off the lights, even in bankruptcy--they deem this "essential services".

I still don't understand the need to light every square foot of our cities/country roads from 1 AM to 5 AM. What pedestrians are out at that hour? If they are in an urban environment, at least every other light might be turned off.

As a side bar - what about all those empty parking lots?

There's got to be a better way to provide the security pointed out in the comments without wasting all those kilowatt hours of electricty.What if streetlights were solar powered - recharging themselves each day? Or had little windmill generators?

Or am I tilting at windmills? Does anyone have any idea what the energy consumption is? I'm assuming it's megawatt dollars not to mention depleting non-renewable energy sources.

kim brings up a good point. The fact is that roads and parking lots already absorb heat energy during the day and radiate it at night. Now, if only this could be easily done with light... Ideas?

While the practicality of this may be debatable on the roads, we could apply this in corridors in office buildings partially lit by daylight during daytime hours. Almost every office environment I've been in seems to have too many lights on 24 X7X365. This could save the environment from a ton of CO2.

It is standard practice in many European countries to have corridor lighting in apartment houses on timers to provide temporary lighting with illuminated pushbuttons. This could probably be extended to street lighting for pedestrians in urban situations.

When the price of LEDs drops to a competitive level with other lamps that will solve the slow warm-up time of streetlamps. Or we could recycle old TVs and computer monitors as streetlights AND signs in a single unit. Light-up signs.

I guess it gets down to this. Does a light (or heating/cooling) load serve a significant purpose? If not, shut it off until needed. A study would need to be done to support such an action and not just do it because we think it is a good idea. Perhaps the local economy is stimulated for various reasons well in excess of the lighting costs, which would justify keeping them turned on.

Another idea would be to install low-power marker lights instead of high-power broad area lighting. That way roadways are marked well and the cost of lighting is all but insignificant. An LED bulb has an average life of 12 years (think about the labor and vehicle usage savings) and you can have 8,000 of them using the same power that 1 large sodium vapor lamp pulls. A solar cell and battery could easily provide all the power needed for ALL the LEDs at an area of concern, anywhere. This same system could incorporate a small camera (cameras can see in the dark) and transmitter to periodically send a picture to local police dispatchers to enhance area security. Thus reducing the mechanical demands upon police vehicles and increasing the surveillance of a city.

As a dark-sky advocate and a rural-living person, I don't understand the overuse of streetlights. They seem to me to be one of the biggest waste's in our society.

I yell at my kids for leaving a 100 watt light on in their room for an hour when they're not there, but the city leaves ten thousand five hundred watt lights on all night.

I know that people have this perceived safety thing, but I figure if I were a mugger, I wouldn't want to do it in the dark? I might trip, you know. Also, I gotta see if the victim is pulling a gun. I need those lights. Ever see a thief with a flashlight? He has to carry the stolen car stereo with one arm.

Wow! I'm impressed. So ypu're saying we need to install motion sensors so that the lights remain off unless motion is detected. Outstanding idea! I'm assuming the cost of motion detectors and installation would more than be offset by the savings in lighting. Anybody have a reason to disagree with this idea?

This is one of the most energy wasteing systems on the planet. There should be an X Prize competition for the people who can come up with a cheap, realistic, security and accident proof system that would switch all those lights off when not needed. 10 million would be a great incentive for clever engineers to design such a system. Surely if we can get to the Moon or Mars, it can be done.