[ROVERNET - UK] LIGHTS and brains

David Read defender110 at ozemail.com.au
Thu Feb 15 09:23:47 GMT 2007

Gundry, Kenneth wrote:
>  Unusually, I will jump in here with my pet hates.  Normal headlights,
> operated by daylight with good visibility (rain or no rain), do no good
> whatever, but occasionally can be dangerous because they prevent one
> from seeing something just beyond them, like a child stepping out behind
> a car.  California recently made it compulsory to turn on the headlights
> when the windshield wipers were in use, irrespective of lighting
> conditions; I wonder how many accidents have occurred as a direct
> result.  Proper low-intensity running lights are a different matter;
> they may be innocuous but generally serve no useful purpose apart from
> the profit to the manufacturer.

I think I have aired this before, but here on the long, straight, 
relatively narrow bitumen outback roads, it is sometimes difficult to 
judge through the heat haze if the vehicle on your side of the road 
ahead is travelling towards (overtaking) or away from you.

Driving with headlights on at least gives other traffic a clue if they 
are looking at your front or rear.

> Directly related, in my childhood, driving from London to Redhill in
> Surrey, the street lighting for much of the distance was sodium
> (yellow).  Then there was a stretch of mercury (blue) and only then did
> you discover that it was foggy!

The wavelength of the yellow sodium light is almost at the human eye's 
maximum sensitivity - our eyes "see" it better.
Unlike blue, it is not scattered easily and so penetrates thru fog more 
readily and does not dazzle you with reflection from the fog's water 

Importantly, with greater penetration, other vehicles can see *you* 
approaching better as well.

<back to my medication ....>

South Oz

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