| Re: Car LED tail lights strobe rate too slow [message #781527] |
Sat, 15 July 2006 05:40 |
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"Daniel J. Stern" wrote:
>
> Pete C. wrote:
>
> > The flicker also attracts attention better.
>
> I keep fairly close track of the international research in the field,
> and I haven't seen any studies demonstrating that flicker of the type
> under discussion, whether perceptible or not, contributes to the safety
> performance of automotive lighting devices. Can you please provide some
> references? I ask because this sounds like one of those marketeering
> claims (compare "HID headlamps produce light that's closer to natural
> sunlight!") with no basis in even theoretical human-factors science.
I think this is a reference to peripheral vision's increased sensitivity
to movement. Google found this: http://www.eyetec.net/group3/M12S1.htm
I think the idea behind most of these products (flickering motorcycle
headlights, etc.) is to take advantage of this effect. I'm not sure how
much real science some of these manufacturers have done (selecting the
correct rate and duty cycle) to justify their claims.
The PWM frequency used to dim taillights seems to be too high to be
designed to take advantage of this effect. Also, a continuous flashing
wouldn't seem to be as effective, as the human brain tends to suppress
repetitive stimuli. The latest LED (and strobe) cop lights are going to
randomized flash patterns to overcome this.
--
Paul Hovnanian mailto:Paul [at] Hovnanian.com
------------------------------------------------------------ ------
"A doctor can bury his mistakes but an architect can only
advise his client to plant vines." -- Frank Lloyd Wright
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| Re: Car LED tail lights strobe rate too slow [message #781528 ] |
Sat, 15 July 2006 06:09 |
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Paul Hovnanian P.E. wrote:
> > > The flicker also attracts attention better.
> > I keep fairly close track of the international research in the field,
> > and I haven't seen any studies demonstrating that flicker of the type
> > under discussion, whether perceptible or not, contributes to the safety
> > performance of automotive lighting devices. Can you please provide some
> > references?
> I think this is a reference to peripheral vision's increased sensitivity
> to movement.
I don't agree; movement =E2=89=A0 flicker.
> I think the idea behind most of these products (flickering motorcycle
> headlights, etc.) is to take advantage of this effect. I'm not sure how
> much real science some of these manufacturers have done (selecting the
> correct rate and duty cycle) to justify their claims.
You're more charitable (or at least more diplomatic) than I am; I'll
come right out and say it: Most of this homebrew nonsense =E2=80=94 flashing
CHMSLs, blinking amber "deceleration lights", motorcycle "headlamp
modulators" and the like =E2=80=94 are all marketeering with zero science
behind them. Unfortunately, regulation of vehicular safety equipment in
North America is often more about politics (who shouts the loudest)
than about actual safety performance. So, we get public transit systems
installing "deceleration lights" on their buses without a shred of
evidence they help anything. We get the same motorcyclist foundations
that baselessly parrot stupidities like "Loud pipes save lives!"
lobbying for -- and getting -- permission to flash their headlamps with
"modulators" all day and all night. We get completely unregulated
aftermarketeers selling kits to make your car's CHMSL flash. All with
plenty of hype and commonsensical-sounding but thoroughly unscientific
babble about why each of these is the next great safety breakthrough.
DS
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