Re: brighter headlights
I seem to remember from some lectures at Uni that light is, like sound, one of those things the human brain does not read entirely logically.
I think the example was that two candlepower was twice the brightness of one candlepower, yet the human eye/brain detected it as only 30% brighter. I'm fairly sure the bulb labels would measure it in absolute, not sensory-corrected, terms.
Anyone know with more accuracy? Heaven knows why I recall this - I did a history degree and a few modules in Psychology as we had to do a third of our course in other departments for some odd reason - it was a psychology module where we were taught this. I think the 30% thing is right, might be talking cack though!