Flashing brake lights.

[-Virgil-]

I have seen the same thing on a jeep and a couple other newer cars.. I always thought it was that way from the factory.

It was not.

Why would this be illegal? Because it's too distracting??

Read post #4 in this thread.

 

[dc38]

I've seen the lights in question. The flashes happen in a span of less than a quarter of a second with the solid red kicking in, and human reflexes are on average 2/10 of a second. It should be safe to assume within reason that people will see the rapidly blinking lights and start to slow down, at the very least. It's not a slow blinking as if the person is signalling SOS on their brakes. I'm not sure what their original purpose was, but I can say that for some cars that have factory standard brighter brake lights, it's hard to tell whether they're braking or just cruising at night. There's a compliance with the max brightness that a brake light can be, but the modern cars seem to be cranking it higher and higher when the car is just idling. (Brakes actuated on a pre-2006 vehicle will be as bright as a post 2006 model on idle). Perhaps blinking lights compensate for that difference?

 

[-Virgil-]

actually in reality it is not that confusing

That may be your personal opinion...but that's all it is, it's not a fact. Lots of people have lots of opinions on how car lights should work differently than they do. Fortunately for all of us, Human factors research and crash data analysis -- not unsupportable personal opinions -- are used as the basis for vehicle safety standards. The standards aren't as perfect as we might like, there's usually room for improvement of one kind or another, but at the very least, potentially unsafe lighting displays are mostly excluded.

flashing happens fast, and only by stop lamps, and

...and meanwhile you have to think about what it is you're seeing and what meaning you're supposed to derive from it. Even if that thinking happens so fast you're not really aware of it, it's extra time before you can initiate the process of lifting your foot off the gas pedal, placing it on the brake pedal, and applying pressure to slow your car. That extra time can very easily mean a crash happens that could have been avoided. This is why car lighting displays are highly standardized. It's also why the latest research on the subject shows a car with red rear turn signals is significantly more likely to be struck from behind than a car with yellow rear turn signals.

as for what do you do when you see flashing lights in front of you?? well it is pretty simple YOU STOP.

For many years this was more or less NHTSA's response to complaints about red turn signals: "Just assume a red light is a brake light". Then they actually did the research and found out that was not correct advice. See the graphic on page 5 of this DOT publication.

 

[Lynx_Arc]

We used to have mandatory vehicle inspections for a long time they were every year then every two years, then every 4 years and now we no longer have them for over 10 years now. Because of this I have seen many vehicles with one or even 2 brake lights out sometimes they would only have one side brake light working and if it did the flash thing you wouldn't know if it was a turn signal or not till it got steady. I agree with most here that the flashers do get your attention but for the most part you aren't thinking about braking till they stop flashing and if that car suddenly slowed down very fast during this time it would have you hitting your brakes harder than usual if you were not completely paying attention. In other words they are more likely to confuse distracted drivers than alert them. Some drivers watch brake lights when distracted others watch the car itself to see if it is slowing down in speed. If you are watching the car in front of you for distance instead of brake lights the flashing would draw your attention away from the distance of the car ahead of you to the light itself for that instant. When I am driving I sometimes allow a good distance in front of me so I don't have to be as watchful of the driver ahead I have plenty of time to slow down and react even if they would be in a wreck ahead I could most likely stop in time.

 

[Alaric Darconville]

I've seen plenty of these lights, usually on Dodges, and most all of them from a particular dealer.
I don't need to see them on a Camaro to know that they are just as bad an idea as they are on Dodge Darts, Calibers, Chargers, and Challengers, as well as on Ford Explorers and the Hyundai Santa Fe. It's not that their implementations were poor on the vehicles that I have seen, it's that the concept itself is bad. This is not an assumption, this is simple fact.

Whether this product is from PulseProtects or J.C. Whitney or Küryakin or the Lillian Vernon catalog, whether it "pulses" three or four or 8 times is immaterial. It's not a good idea.

To substantiate such a claim: http://www.gpo.gov/fdsys/pkg/FR-1998-11-04/html/98-29520.htm



You might reread this post again to see why this is a bad idea.

 

[alpg88]

yes, it happens fast, 3 fast strobes, than solid bright light

 

[-Virgil-]

I've seen the lights in question. The flashes happen in a span of less than a quarter of a second with the solid red kicking in

We've got a variety of different lights being discussed in this thread. This description sounds like you're talking about the stop lights on some fire trucks and ambulances.

and human reflexes are on average 2/10 of a second.

The link you seem to be trying to make, that a brief flash of a stop light before it begins burning steadily is OK if it's equal or shorter in duration to this 0.2 second figure, is not supported.

It should be safe to assume

It is not.

people will see the rapidly blinking lights and start to slow down, at the very least.

No. See post #23.

some cars that have factory standard brighter brake lights, it's hard to tell whether they're braking or just cruising at night. There's a compliance with the max brightness that a brake light can be, but the modern cars seem to be cranking it higher and higher when the car is just idling. (Brakes actuated on a pre-2006 vehicle will be as bright as a post 2006 model on idle). Perhaps blinking lights compensate for that difference?

There is no basis for thinking flashing (or "blinking", "pulsing", etc.) stop lights will compensate for what you're talking about. Moreover, the intensity requirements for stop lights and rear position (tail) lights have not changed in many years. There is an allowable intensity range for the stop light function, and there is a very different allowable intensity for the rear position (tail) light function you are calling "just idling". There is no overlap between these intensity ranges, and just to make sure, there is also a requirement that a combination stop/rear position lamp put out 3x more light in the bright (stop) mode than in the dim (position) mode, except at certain extra-critical viewing angles where the stop light must put out 5x more light than the position light.

 

[dc38]

There is no overlap between these intensity ranges, and just to make sure, there is also a requirement that a combination stop/rear position lamp put out 3x more light in the bright (stop) mode than in the dim (position) mode, except at certain extra-critical viewing angles where the stop light must put out 5x more light than the position light.

Are you sure? The apparent brightness of the new tail lights (stock cadillacs and American cars) is MUCH greater than slightly older cars. As for the blinking lights being a hindrance rather than a help, I do see point. The question is, then, why would these things be offered aftermarket at the place of purchase? Confused...

 

[Alaric Darconville]

Are you sure? The apparent brightness of the new tail lights (stock cadillacs and American cars) is MUCH greater than slightly older cars.

He's sure. What may make them look brighter (other than perhaps being slightly brighter, but still within the limits described, such as the major/minor ratio) is that the LEDs emit entirely red light, rather than having a white light bulb (and a lower-powered filament with low filament luminance) behind a red lens.

why would these things be offered aftermarket at the place of purchase?

Because that makes the dealer even more money. Especially if the buyers are financing and figure they can afford $150 "over 5 or 6 years" with the financing. Money makes the world go 'round!

 

[-Virgil-]

Are you sure?

Quite certain of it.

The apparent brightness of the new tail lights (stock cadillacs and American cars) is MUCH greater than slightly older cars.

The range of allowable taillight intensity for the "tail" (rear position) light function is 2 to 25 candela. For a stop lamp, it's 80 to 420 candela. These are the axial (straight back from the lamp) intensities; lower minimum values apply at various angles but the maximum is never higher than the axial value. This range of values covers the whole range of possible configurations. The 3:1 and 5:1 ratio rule applies, too.

You're sharp to use the phrase "apparent" brightness. That's the key to what you're seeing. LEDs can create the subjective impression of higher brightness for any given intensity -- the degree of this effect depends on the specific LEDs and optics, and how the LEDs are driven. In many cases they're not fed steadily, but are rapidly pulsed at full voltage and current; persistence of vision (the same thing that makes animations appear to walk and talk and move) causes us to see such lights as dim -- except if they pass quickly across our gaze, then we can sometimes see what is called the "beads effect". Anyhow, research is continuing into whether the different brightness impression of various kinds of lights producing the same intensity might mean the regulations need to be adjusted, but for now the intensity range and ratio requirements are doing a pretty good job.

As for the blinking lights being a hindrance rather than a help, I do see point. The question is, then, why would these things be offered aftermarket at the place of purchase?

Because enforcement is lax. There is a vast amount of unsafe and illegal vehicle equipment very easily available. You can get it on amazon and a zillion other internet sites, you can get it at parts stores or Wal-Mart, and some vendors have made a specialty of marketing through dealers (you tell the salesman "Ooh, no, sorry, I'd really rather we order the car from the factory; this one is almost what i want but it doesn't have the HID headlamps" and the salesman comes back with "No problem, buy this one and the service department will put in an HID kit for you").

 

[markr6]

Are you sure? The apparent brightness of the new tail lights (stock cadillacs and American cars) is MUCH greater than slightly older cars.

I've noticed that on new cars as well. The stock brake lights are very bright. I never had to squint from tail lights in the dark before. Just last night I jokingly put on my sunglasses when my wife also commented on it. I don't remember the car, maybe an Audi? But I've notivced this on more than one make/model. The entire interior of my Jeep glows RED!

 

[dc38]

I've noticed that on new cars as well. The stock brake lights are very bright. I never had to squint from tail lights in the dark before. Just last night I jokingly put on my sunglasses when my wife also commented on it. I don't remember the car, maybe an Audi? But I've notivced this on more than one make/model. The entire interior of my Jeep glows RED!

Although the lights leave me seeing blue spots afterwards, the red glow (for some reason) is kinda comforting when stopped in the cold at a light...

 

[SemiMan]

Scheinwerfermann,

If I remember correctly, the measurement for intensity of the brake light (all lights) is only done at a single nominal temperature.

Red leds have a significant increase in efficiency at cold temperatures. Perhaps some of the perception of increased output could be related to this, I.e. cars in cold climates in winter.

Anecdotally I have noted some amber led turn signals appearing very bright on a cold night.

Semiman

 

[Optical Inferno]

Scheinwerfermann,

If I remember correctly, the measurement for intensity of the brake light (all lights) is only done at a single nominal temperature.

Red leds have a significant increase in efficiency at cold temperatures. Perhaps some of the perception of increased output could be related to this, I.e. cars in cold climates in winter.

Anecdotally I have noted some amber led turn signals appearing very bright on a cold night.

Semiman

From the SAE testing it should be done at 25C in an environmentally stable testing chamber.

You are also right about red and amber LEDs getting brighter with the cooler temps. If you look at most datasheets the red and amber LEDs have a much "steeper" drop off of intensity vs. temperature. So this works in reverse, the cooler they get the faster they rise in intensity.

With the implementation of PC (phosphor converted) amber LEDs and potentially PC red LEDs, this may eventually become less of an issue in the future as blue and white LEDs do not fluctuate as much in their intensity with temperature change. Just have to get the price down on the phosphor converted LEDs.

 

[-Virgil-]

That's an interesting point, Semiman. I thought there was something in SAE J1889 addressing the temperature/output dependence, but I'm not finding it; the provision I have in mind may be located elsewhere (or it may exist only on my mental "wish list"!). I'll check into it.

 

[SemiMan]

Have not directly worked with customers in automotive in some time. I am fairly certain in approximately 2004-2005 no provision existed though it was discussed.

At the other end of the spectrum is hot days in Arizona and low output.

Semiman

 

[-Virgil-]

The issue of reduced output with increased temperature is definitely addressed in J1889.

 

[alpg88]

any led datasheet shows about 20% difference in brighness for cold vs hot die.

and 20% loss in brighness does not look like anything dramatic, actually human eye might not even catch the difference.

so i doubt hot climate has anything to do with modern cars lights being bright or not so bright. i'm more inclined to think it has to do with light design. and wide range standarts.

some cars, like 06-07 accord sedan has leds in the tail, and they blind if you stop behind such car at night. i would still see all the leds and could even count them after i close my eyes, they would temp. burn in my retina, summer or winter, does not matter.

 

[-Virgil-]

any led datasheet shows about 20% difference in brighness for cold vs hot die.

This kind of generalization doesn't really get us anywhere helpful.

and 20% loss in brighness does not look like anything dramatic, actually human eye might not even catch the difference.

It can make the difference between a compliant vehicle lamp and a noncompliant one.

i'm more inclined to think it has to do with light design. and wide range standarts.

You're probably right about that.

 

[SemiMan]

any led datasheet shows about 20% difference in brighness for cold vs hot die.

and 20% loss in brighness does not look like anything dramatic, actually human eye might not even catch the difference.

so i doubt hot climate has anything to do with modern cars lights being bright or not so bright. i'm more inclined to think it has to do with light design. and wide range standarts.

some cars, like 06-07 accord sedan has leds in the tail, and they blind if you stop behind such car at night. i would still see all the leds and could even count them after i close my eyes, they would temp. burn in my retina, summer or winter, does not matter.

That generalization only applies to InGaN leds .. Blue green white. It does not apply to AlInGaAP leds .. Red and yellow where 2 or even a 3x hot cold is possible.

Semiman