Toyota switch from LED vs. incandescent

turbodog

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I took the time to read the study, the whole thing. It's 9 years old... Things tend to improve, and the study admits limitations to the data analysis due to lacking the ideal samples (mid year changeover). Am sure more data and further studies will come out.

As far as the ramping down to off... incan allows for a more gradual dimming... giving an indication that something's changing. Leds just 'slam the door'... and if you miss/blink in the instant they turn off, you've missed the cue.
 

turbodog

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I had to think about it a bit, and it's probably not what turbodog was thinking of, but brake lights that were to delay 2 seconds before turning off would do nicely to smooth out the erratic blinking from the drivers that are neurotic about the brake pedal.

That would negate the ability to quickly tap your brake lights... signalling that you are stopping suddenly, or that upcoming traffic has changed dramatically.
 

alpg88

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I had to think about it a bit, and it's probably not what turbodog was thinking of, but brake lights that were to delay 2 seconds before turning off would do nicely to smooth out the erratic blinking from the drivers that are neurotic about the brake pedal.
That would be a bad idea. this erratic braking, is a warning, the driver in front may not be adequate, pull back, or pass. You never know, brakes may not the only thing that driver uses erratically.
 

Alaric Darconville

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but brake lights that were to delay 2 seconds before turning off would do nicely to smooth out the erratic blinking
Oof, no. This is a bad idea. They need to be on when on and off when off, no delay off. This isn't a cornering lamp, it's a stop lamp.

Yes, it's annoying when people seem to step on the brake at random, but a delayed off is bad (such as when the driver is frenetically strobing them because they see the pileup ahead and want to warn others).
 

John_Galt

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Regardless of LED v Incan taillights... can we fix the issue of people driving with their left foot on the brake? It's really cool to see someone accelerating from a stop, or dipping in and out of traffic, with their brake lights lit up full blast.

You'd think frequent brake pad replacements would be an indicator something is wrong...
 

-Virgil-

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I took the time to read the study, the whole thing. It's 9 years old
Yes, it is. That, however, does not necessarily invalidate it.

Things tend to improve

Not necessarily. As previously mentioned, automakers are using the increased efficiency of LEDs to make tail lights (stop lights, turn signals, headlamps) smaller and smaller for styling reasons. As a result, photometric performance is not improving, and in a significant number of cases it's actually decreasing.

What is it you imagine has improved in the nine years since that study was done?

and the study admits limitations to the data analysis due to lacking the ideal samples (mid year changeover).

Well, yes. The study doesn't say LED stop lights aren't better, it says no such conclusion was reachable given the data set studied.

Am sure more data and further studies will come out.

I'm not so sure. Incandescent stop lights, as a class, are disappearing from new car designs (and facelifts/refreshes, etc). And -- again -- manufacturers are aggressively restyling lights so they are fast moving away from the sizes and shapes of traditional (incandescent) lights. Seems to me like every day that passes is that much harder to compile a data pool of incandescent versus LED stop lights that are otherwise closely similar. That 2013 study might very well have been the last, best shot at that kind of study.

UMTRI did another study just last year, which, given the difficulty in finding "all other factors equal" vehicles to compare crash data for, is probably the best technique to find answers to this question. They modified cars with LED stop lights so that the stop lights behaved either normally (instant on/off) or like incandescents (250 ms rise/drop time). The stop light behavior was randomized beyond the driver's knowledge or control, and the instrumented vehicles (data loggers, rear-looking cameras and radars) were driven at the posted speed limit (= people gonna tailgate) in actual traffic for six weeks. Result: no benefit to instant-on versus incandescent-type rise time.

As far as the ramping down to off... incan allows for a more gradual dimming... giving an indication that something's changing.

Last year UMTRI did quality research on sequential turn signals of various types; they compared the effective conspicuity (speed and accuracy of grokking the message) of sequential-on, sequential-off, LED and simulated-incandescent conventional on/off, and two kinds of "moving spot" turn signals (whole lamp lights up, and a brighter spot moves across the width of the lamp). Results: the instant on/off LED turn signals were better than the fade-on/fade-off incandescent signals; the sequential-off signals were better than the static LEDs, the sequential-on signals were better than the sequential-offs, and the moving-spot signals were better than the sequential-ons.

That, plus the stop light study with instrumented cars in traffic, pretty well puts to bed the idea that ramping down the stop lights is helpful (or harmful).

Leds just 'slam the door'... and if you miss/blink in the instant they turn off, you've missed the cue.
I don't think so; there's a car in front of you without its stop lights lit -- that's what you need to know; it's less important (maybe not important at all) to know whether the driver took his foot off the brake half a second ago or half an hour ago.

I used to think some fade-time on LED turn signals might be a good idea (instant-on, fade-to-off), for pretty much exactly the same reason you describe: increase the effective conspicuity of the turn signal by increasing the likelihood of a momentary glance being enough to detect there's a turn signal operating. Then along came Mazda's CX-30 doing exactly that (see video above), and yuck, its turn signals seem a whole lot less conspicuous because of the fade-to-off dilutes the state-change. It looks a lot less like a turn signal, and a lot more like a steady-burning amber light that intermittently briefly flickers off. I think the problem is too long a fade-to-off time. If it were cut in half, to be more like an incandescent bulb, I think it would probably be fine. But as per the recent UMTRI research, it likely wouldn't help anything versus an instant-on/instant-off LED turn signal.
 

-Virgil-

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brake lights that were to delay 2 seconds before turning off would do nicely to smooth out the erratic blinking from the drivers that are neurotic about the brake pedal.
This right here is a great illustration why lighting regulations have to be based on good research and sound science. People come up with all kinds of random ideas for "improvements", and they're really sure it'll make everything safer and better. Most of these ideas, if put into practice, would really do the opposite. Including this one.
 

turbodog

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...


Well, yes. The study doesn't say LED stop lights aren't better, it says no such conclusion was reachable given the data set studied.


...

It said it as a class, but the honda data alone was definitive and compelling.

And I crossed over between stop/turn. I'm a proponent of a fading turn signal... especially as some people only give 1-2 blinks before/as they are moving lanes.
 

-Virgil-

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It said it as a class, but the honda data alone was definitive and compelling.

"Definitive and compelling" strikes me as reading more into the results than they actually show. "Interesting and suggestive" is about as far as I'd go. The study says:

The main analysis for the 2006 Honda Accord coupe and sedan alone found a statistically significant 7.3 percent reduction in rear impacts (...) Even though the Honda Accords stay in the same generation, it is evident that they are not "clean" switch pairs because the switch to all-LED was accompanied by a revision of the rear-lighting configuration. For the coupe, the CHMSL changes from being inside the car to the outside on the trunk. The sedan changes more extensively from having lights/reflectors on the trunk to only having the lamps on the side. And like the coupe, the CHMSL changes location from inside to outside for the sedan. All these changes might affect the conspicuity of the lamps and how drivers of the following vehicle react to them (...) Table 3 does not address other issues, such as the effect of the change in the rear-lighting configuration, or even the possibility of an unexplained market shift for Honda Accord in 2006 that resulted in a different group of drivers with different crash patterns (...) even though the analyses of crash involvement rates for all vehicles resulted in positive effectiveness (because LED was effective on the highest-sales make-models such as Honda Accord), that result may be questioned because the majority of switch pairs did not improve with LED.

And that's without even mentioning other changes. For example, the incandescent stop lights on the pre-'06 Accord sedan look like their installed height is lower. And we don't have photometric data for the incandescent and LED Accord stop lights; it's entirely possible (I would say it's highly likely) the LED stop lights on the '06-'07 Accord have higher intensity and higher luminance than the incandescent stop lights on the '04-'05 Accord. Higher intensity is correlated with improved conspicuity at longer observation distances; higher luminance at shorter observation distances.

And the study concludes:

We are unable to draw any meaningful conclusion because our database did not include a single make-model that switched from incandescent to LED or vice-versa without other simultaneous major changes. The study could not analytically isolate for the change in light source, but may have captured other factors that occurred to the make/models during the switch from incandescent to LED. These other factors include the potential effects of major changes in the rear-lighting configuration (such as moving the CHMSL to a more prominent location) as well as the consequences of major vehicle redesigns, which can change both how the vehicle performs and what sort of people buy it. As of now, the real-world crash data does not demonstrate that LED stop lamps and LED CHMSL are more beneficial than incandescent lamps, but also fail to rule out such a possibility.

So no, I really don't think it's accurate to call that Honda data in this study definitive or compelling. Keep in mind that plain old risk homeostasis could easily be cancelling out the theoretical benefit of instant-on stop lights.

I'm a proponent of a fading turn signal... especially as some people only give 1-2 blinks before/as they are moving lanes.
OK, you guess/assume/think/wish/hope a fading turn signal is better. So far the data (last year's UMTRI study) says it's not, though. We'll have to wait and see as more data amasses and is poked and prodded. Here's something to chew on, though: faster flash rate is significantly correlated with better conspicuity. Like, much faster flash rate than presently allowed, up into "hyperflash" territory. Maybe turn signals should flash much faster, which would address the issue you describe (only brief activation of the signal).
 
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