Posted By: tonyHow tall should a lamp post be, ie how high above a road or pavement should a luminarie or light be?

The higher up they are the brighter they need to be and the more energy they use

The inverse square law applies to the levels of light suggesting the lower the better.

The cost of the posts and the number of standards tends to suggest that there should be fewer and taller.

I have seen shorter ones (under flight paths of planes) closer together working well.

anyone want to have a stab at the perfect height for today? I can believe that in the seventies tall was OK but is it still best?

I don't believe some of that is correct. I don't think light attenuates in the way you describe. The brightness may fall off as the square of distance but that's because the light is spread out over a greater area not because of losses caused by it travelling through the greater distance.

Not really Ed - the luminaire photometry will address that - many lanterns have adjustable lamp holder positions so you just toe in or out depending on actual height - although I agree with you broad comment

to answer the initial qusetion, as Ed points out height is academic to energy consumption, and over life, taller columns with greater spacing is more economic from a construction perspective

The biggest saving would come from replacement lanterns with dimming capability and then impose a part night low output (or off) curfew, coupled with better quality light that allows generally lower illuminance levels to achieve the same effect

Regards

Barney

Was there not something about the spacing of streetlights in towns that denoted the speed limit, seem to remember if they are within 100 yards of each other then it is 30mph. May just be one of those urban legends like you can drink 3 pints of real ale, then a pint an hour and not be over the DD limit.

There are too elements to an accident, the probability of having one (probably higher in unlit areas) and the consequences of having one (probably less if going slower). Then there is the driver element, youngsters are more likely to have an accident than sensible people like me.
Personally I hate street lamps, they used to attract the kids late at night so they can call their dealer.
I read somewhere that a local authority is being sued for an accident where they had turned the lights off. Either way the tax payer is going to have to pay for that.
As for height, how about lower and less powerful and no closer that 300m on a normal road. More at 'tricky' junctions, none at roundabouts or where traffic lights are situated, most drivers can handles these, and there are nearly always warning signs anyway.

<blockquote><cite>Posted By: Joiner</cite>Pedestrians?<img title="" alt="" src="/forum114/extensions/Vanillacons/smilies/standard/cry.gif"></img></blockquote>

Be cheaper to issue free torches to all than run street lights.............

Posted By: JSHarrisBe cheaper to issue free torches to all than run street lights.............

Over-use of street lights destroys a pedestrian's dark-adaptation. You can actually see better with fewer/dimmer/no street lights than with the bright ones that have become the penchant recently. Contrary to popular belief, crime-rate is not reduced by adding street lighting.

There's a big campaign over here to restore dark skies - google "megantic dark sky reserve" for an example of what is being done over an area of 8000km2 to reduce street lighting.

Paul in Montreal.

OK. You're walking down a poorly-lit street towards a group of hoodies lounging either side of the footpath. Be the same whether it was brightly lit or as is, but which situation would you feel less secure in? And if you were a woman? Or had a daughter you knew was going to have to walk that route?

Bit like the old dear whose story is/was going the rounds on the internet. Stopped by a Highway Patrolman, she was found to have a permit to carry a concealed weapon. She had guns all over the car as well as in her handbag. When asked by the patrolman what she was afraid of she replied: "Not a damned thing!"

Posted By: tedLamp-posts should be tall enough to safely swing a politician from. Anything more is a waste.

Can we add bankers? Is the average banker taller or shorter than a politician?

Your school had text books????

I find that when street lights are lower, they tend to glare as I'm approaching them. Would there be a benefit in making them lower and angling the head to face the direction of traffic?

Brian.

Is that a running a street light cost for each one?

Posted By: DamonHD"He uses statistics as a drunken man uses lamp-posts... for support rather than illumination."

Yep

What sort of power are typical street light bulbs if they only cost £30 a year to run, then?

A quick web search seems to show that typical low pressure sodium street light bulbs are around 180 W. For street lights that are on all night, all year around from dusk to dawn (with light-activation), they are going to be on for somewhere around 3,300 hours a year, at a guess. This means that energy consumption will be around 600 kWh per year or thereabouts for each street light.

If that £30 a year running cost was just for electricity, then it means that councils are only paying about 5p per unit, is that right?

If bulb replacement is the main running cost, then it looks like councils must be paying a lot less than 5p per unit for electricity.

Something seems off here.

But if bulb changing is the biggest running cost element, then that implies more than 50% of that £30 a year, which makes the electricity cost less than 2.5p per unit. AFAIK, councils are VAT registered and have to pass on the VAT from costs incurred, although presumably street lighting electricity is on the low rate anyway.