Speaking of LED lighting Lancashire County Council have been going for this in a big way in the previous few months installing WRTL Stelas on quite a few estates which were built in the last 15 years and therefore are quiet cul-de-sacs which already have metal columns to retrofit the Stelas to post-top. I think they look quite good on modern estates and the columns were already painted black so they match the lanterns. How good they'd look on a 1930s estate retrofitted to a sleeved concrete column (if that's possible) or on one of those awful unpainted Stainton 'Bones' columns they tend to use now I don't know however!
These Stelas have been springing up overnight and I will have to try and count the LEDs in them next time I see one but the lighting levels from them are appalling! The old mercury lighting was better than this! The previous 50w SON used on these roads was definitely better than this! I'm sure they're saving the council a lot of money though, probably all they're concerned about!
As for lantern dimming not being 'detectable to the human eye' I beg to differ. I live on a main A-road which has 150w Vectras lighting it. When at full power these light the road extremely well. However after midnight the Vectras are dimmed to a considerable level and look like they're using 70w. On a quiet road this may be acceptable but on a road like mine with through-traffic all night it isn't as the lighting levels are again, terrible. I noticed when we had some fog recently that these dimmed Vectras barely cut through it! Lighting levels are going back to what they were in the 1930s with all this cost-cutting! As sotonsteve says they should use CFL and CPO and it would be much brighter for the same or less energy effiency!