Speed perception and Headlights

No I dont want a new debate....

A friend needs to find some documents about how the use of headlights tends to make others misjudge their speed and judge their speed to be higher..

I have tried search but there is so much stuff listed I cant find what I am looking for..

anybody have any links to official documents ( as opposed to personal experiences) which show that people over estimate speed of vehicles with bright lights on??

TIA

PS needed rather urgently

Good luck.

Originally Posted by Baketech

Google "crypsis by counterillumination".

Thanks but I am not after info about camouflage effects.. quite the opposite.. it was an article where it was shown that people judged bikes with headlights on as going faster than ones that were not displaying lights...........

Check my recent thread in SA, read the report, it may be m ed ntioned /refernced there

Also, search for posts by me, include ovrr- under- estimation speed. Try search for hills too.

Originally Posted by Gedge

Thanks but I am not after info about camouflage effects.. quite the opposite.. it was an article where it was shown that people judged bikes with headlights on as going faster than ones that were not displaying lights...........

I can't remember any details, but I think there was a cross-over (poss. 30mph) where there was under-estimation with light below 30 and over-estimation above.

Shaw 1979

Compared the accuracy with which subjects estimated the speed of a motorcycle with headlamp on, and off.

Subjects over-estimated the speed for lower speed of approach
Subjects under-estimated the speed for higher speed of approach

The reversal from over- to under- took place between 50-55mph with the headlamp off, and between 35-40mph with the headlamp on.

Now tell us where you C&P it from

Originally Posted by Horse

Now tell us where you C&P it from

You either here, the other place or an email. Not from the source document sadly.


But maybe items 11 & 13 HERE are relevant to the OP