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View Full Version : Are turn signals brighter than brake lights?


Aaaaaaaaaaaaaaaargh!
10th Dec 2007, 03:37
Many's the time I've been sat at a light and the car in front of me has the brakes on. Sometimes they want to turn also, so they put the signal on and then I get almost blinded.

I figured someone must know, but are turn signals brighter than brake lights?


:zzz:

makintw
10th Dec 2007, 03:48
Thought they were both the same wattage.

Have yet to figure out why the Yanks use red for indicators - daft me thinks.

Howard Hughes
10th Dec 2007, 03:50
Next you'll be asking, are the ads louder than the programs...;)

G-CPTN
10th Dec 2007, 06:19
the car in front of me has the brakes on. Sometimes they want to turn also, so they put the signal on and then I get almost blinded.Could it be that you are experiencing twice the wattage?

Buster Hyman
10th Dec 2007, 07:15
Well...you could always stop tailgating.

ww1
10th Dec 2007, 07:24
and, come to that, the ads ARE louder than the programs.

Thai Pom
10th Dec 2007, 07:26
I don't know. I have never seen a Thai Driver use one !!

ZFT
10th Dec 2007, 07:30
Only when they overtake and are exactly alongside of you, then they signal left!!!!!!!(Rules of the road are to drive on the left)

DX Wombat
10th Dec 2007, 07:31
are turn signals brighter than brake lights?
What are they? :confused::confused::confused:

UniFoxOs
10th Dec 2007, 09:04
Turn signals (we call them indicator lights here) are the same wattage (21) as brake lights. Only difference is on most cars now there is a "high intensity brake light" at more-or-less eye level, which does tend to blind following drivers considerably. I have never been able to discern the real reason why these are fitted, but I suspect it is so that you can tell that the pillock in front is braking when he has on his high-intensity rear fog lights for no good reason, which are so bright that they make the normal brake light hardly noticeable.

UFOP

west lakes
10th Dec 2007, 09:17
Bulb size is as stated the same so the light output from the bulb (lumens) is the same. However when passed through a coloured lens some intensity is lost see http://en.wikipedia.org/wiki/Refractive_index.

In effect this means that the light appears less intense dependant upon the colour of the lens. (think sun glasses).

The high level brake lights mentioned, i seem to recall, were first tried by New York taxis. The theory is that being mounted in the rear window they are visible through the windows of following vehicles to those further back in a queue. The intent is to give advance warning of braking to prevent rear end collisions.

Aaaaaaaaaaaaaaaargh!
10th Dec 2007, 12:34
west lakes, that was the reason I suspected, namely that they were the same wattage - bulb even, but that the red lens shields the light more the the orange ones did.

west lakes
10th Dec 2007, 12:51
As an aside, it's interesting to note that vehicles fitted with LED lights do not suffer the same "difference".
As the LED produces the light at a set wavelength (colour) there is no refraction. It also is part of the reason that a lot of high level brake lights seem brighter as they can be LED types.

MadsDad
10th Dec 2007, 13:22
One possible reason for the extra brightness, following up on the 'lens shield' argument below is that brake lights are still a white bulb with a red shield (which will lower the bulb intensity). Indicators now have a clear shield (which will, presumably, lower the light intensity much less) and a yellow bulb. The bulb will, also presumably, emit the required wattage in yellow light rather than emitting white light which will be attenuated by the shield.

AirScrew
10th Dec 2007, 13:26
In the dark, driving behind a set of (constant) red 'tail' lights, you will be much more receptive to the change of light level, rather than the actual level of either the red or yellow light.

But also, the yellow lens (filter) is closer to the frequency of the source (white light (heat)), and therefore allows more light through.

MadsDad
10th Dec 2007, 14:03
Forgot to mention.

The purpose of the high brake light (in the back window or wherever) is to allow drivers behind to see them through intervening vehicles* (by looking 'through' the car in front). They are the same intensity as the 'normal' brake lights.

(* this is for the few drivers who have the wit and intelligence to look what is happening further forward than the end of their nose).

G-CPTN
10th Dec 2007, 14:18
. . . and when White-van-man isn't between them and the other cars.

But also, the yellow lens (filter) is closer to the frequency of the source (white light (heat)), and therefore allows more light through.Not in the US of A where they have red turn-indicator lenses. However, the alternating light-level (and the fact that there are two lamps when both are lit) will overwhelm the eye into reacting against the sudden increased brightness. It's like those optical delusions where straight lines appear to converge or even seem bent.

a yellow bulb. The bulb will, also presumably, emit the required wattage in yellow light I doubt it - the filament (which determines the wattage) will be the same for both clear and coloured bulbs, but the effect of a coloured bulb will not necessarily emit the same number of lumens (quantity of light) as a clear bulb with a coloured lens. I'm not aware of a requirement to measure the 'brightness' of lamp assemblies (although it would be reasonable to expect this) - I was a mechanical chassis engineer, not bodywork and electrics. Those guys walked funny and had limp wrists and squeaky voices . . .

G-CPTN
10th Dec 2007, 14:43
My search for information about lamp intensity has revealed that there are indeed regulations governing brightness:- A: All motor vehicle lamps are required to meet federal specifications regulating the brightness of the lamps. These regulations require that each lamp be designed to meet certain intensity values at various angles. The words "candlepower" and "brightness" are popular terms for the technical term luminous intensity. Intensity is measured in units of Candela, and has no meaning when applied to a lamp as a whole. Intensity can only be measured at specific angles.
The federal regulations for most lamps require that the lamp be tested at 15 to 20 specific angular locations, called test points. At each of these test points, the lamp is required to have a luminous intensity greater than a certain minimum candela value. Often, that intensity must also be less than a certain maximum candela value as well. When evaluating the performance of a lamp, all of these test points must be considered. Looking at the candela value at a single test point is not sufficient to understand the overall performance of a lamp.
However, we oldies have been relying on information related to incandescent bulbs, whereas more and more vehicles are being fitted with light-emitting diodes (or LEDs), so all bets are off concerning the relative intensity of turn indicators and brake lamps.
All Grote lamps are designed to exceed the appropriate federal regulations for their specific functions.
Other factors also play a role in how bright a lamp appears to a driver's eyes. Many people have commented that LED lights seem brighter than standard incandescent lamps. Some preliminary studies indicate that this may be true, and that an LED lamp may appear brighter to a human eye even when it's measured intensity is identical to that of an incandescent lamp.
I bet Herr Drapes can recall when you needed water and some calcium carbide to produce acetylene gas for vehicle lamps before the days of Joe Lucas and his 'King of the Road' devices were introduced.

Groundbased
10th Dec 2007, 14:47
Don't know anything about the technical ins and outs, but find that it is almost blinding to be behind a current model Range Rover in a traffic queue and the brake lights are on.

Combination of them being at my eye level and very bright.

Arado
12th Dec 2007, 12:33
I find it much the same when the Range Rover's BEHIND me: I get blinded just as badly... those xenon lights can really blind one.

27mm
12th Dec 2007, 12:46
Go along with that, the Xenon lights self-level, so having someone behind with them can be tricky, as it looks like they are intermittently flashing you - or maybe they are.......

frostbite
12th Dec 2007, 14:42
I like to think I'm a fairly careful experienced driver, but I shudder to think of the several times I've been waiting to emerge from a side road, been flashed, pulled out and it's been a Volvo which went over a bump in the road.....

G-CPTN
12th Dec 2007, 15:42
The Highway Code cautions against responding to such 'instructions' unless given by a policeman on point duty - or it used to . . .

Edited to add:-
104 You should also
* watch out for signals given by other road users and proceed only when you are satisfied that it is safe
* be aware that an indicator on another vehicle may not have been cancelled

BigEndBob
12th Dec 2007, 18:10
There are very stringent regulations governing lamps on the road in order to meet Highway standards.
I have in the past been tasked with getting traffic lights both tungsten and led through the BSI test centre at Hemel Hempstead. Brightness, chromaticity, anti phantom qualities have to meet a set standard.
Notice how all red/tail and amber turn lights on cars are the same colour as red/amber traffic lights?
On one occasion ahead of me at the test centre was being tested a small front lamp for a bicycle and would imagine the same would happen for car lights.

stickandrudderman
13th Dec 2007, 15:29
I'd like to see a national campaign to stop people sitting in traffic with their foot on the brake.
Not only is it stressful for the driver sitting behind, having to stare at brake lights all the time, but often leads to the bulb holder overheating and melting, causing bulb failure.
Modern Mercs have a function whereby the vehicle will hold the footbrake for you, without you having to apply pressure, which rather compounds the issue.
So: if you're sitting in a traffic jam, put it in park or use the handbrake!
As an aside: I did hear that youngsters these days are tought NOT to use the gears to decellarate, as it reduces the necessity for using the brake, thereby not activating the brake lights and warning other drivers that you are slowing down!:ugh:

ZH875
13th Dec 2007, 15:43
I would also like to see cars fitted with sensors, so that cars which are stopped at the side of the road cannot have their headlights on dip beam, but would revert to sidelights after a short period (So you can see at a junction).

This is to stop cars which have pulled up on the wrong side of the road, facing oncoming traffic, leaving their headlights := on and dazzling approaching drivers.

Peter Fanelli
13th Dec 2007, 15:50
The bulb will, also presumably, emit the required wattage in yellow light rather than emitting white light which will be attenuated by the shield.


The wattage of a light bulb is dependant on the current drawn and the voltage applied. It has nothing to do with the color of the glass enveloping the filament.

I suspect the unit you are thinking about is Lumens

AirScrew
13th Dec 2007, 15:54
Too much technology....whats the fail-safe mode?
What if while I'm waiting a child goes infront of the car, and I cant see it cos I've only got bloody side-lights on?
etcetc

Why not just have the manufactures/dealers adjust the lights correctly, and checked at service intervals........

G-CPTN
13th Dec 2007, 18:43
I did hear that youngsters these days are tought NOT to use the gears to decellarate, as it reduces the necessity for using the brake,Indeed, although I learned to double-declutch and change-down through the gears to slow down the vehicle, the current thinking is that brakes are cheaper than gearboxes, so drivers are advised to reduce speed using the brakes before selecting an appropriate gear. :ugh: (IMO)

ShyTorque
13th Dec 2007, 19:00
Stick, So: if you're sitting in a traffic jam, put it in park or use the handbrake!

I prefer to go into neutral and use the handbrake as required if stopped rather than use "Park". It's not a good idea to put an auto transmission in "Park" in a traffic queue in case the car gets bumped from behind. The transmission is mechanically "spragged" in that mode and it could get badly damaged even in a minor thump.

Also, some automatic 'box equipped cars have an interlock which requires the footbrake to be applied before the car can either be moved either in or out of the "D" or "P" positions. This means the brake lights on an automatic car come on at "strange" times before the car moves off.

If I'm the last car stopped in the queue and there is a gap in the traffic behind, I will sometimes use my brake lights to signal to drivers coming up fast that I am braking / stopped (I sit scanning my rear-view mirror for this, being last in line is a very vulnerable position, especially on a motorway).

If the traffic is moving very slowly, my brake lights will be on much of the time because cars with auto boxes creep forward even at tickover, so continual braking might be needed.

G-CPTN
13th Dec 2007, 20:05
My (Morse-type) Jaguar saloon had a hold-solenoid on the footbrake which held a small amount of pressure until the accelerator was applied. It was sufficient to hold the vehicle on a gradient - provided the Dunlop disc brakes were in good order (when I got the car - secondhand - the pads were worn down to the piston 'stops' - there was no metal backplate to the pads - so no matter how hard you pressed there was virtually no braking effort - new pads restored full braking).

WRT rear view, I've always used the maxim of one-third rear view and two-thirds forward vision when driving - that way you don't miss being tailed or fast-approaching overtakers (as well as that idiot who just isn't going to stop in time).

GrumpyOldFart
13th Dec 2007, 21:02
I'd like to see a national campaign to stop people sitting in traffic with their foot on the brake.
Not only is it stressful for the driver sitting behind, having to stare at brake lights all the time



Not picking on you personally, stickandrudderman, but this is a subject which has puzzled me for years. Tens of millions of North American drivers, almost exclusively using automatic transmissions, and holding their vehicles with the footbrake, never show the least concern. I don't believe there's much difference in the relative wattages and, if anything, North American cars tend to be equipped with more (many more!) bulbs than the typical European/Japanese models. Yet British drivers seem to be paranoid about this. Can anyone explain why?



often leads to the bulb holder overheating and melting, causing bulb failure.


I've never once heard of this in nearly thirty years over here. :confused::confused:

ShyTorque
13th Dec 2007, 21:12
WRT rear view, I've always used the maxim of one-third rear view and two-thirds forward vision when driving - that way you don't miss being tailed or fast-approaching overtakers (as well as that idiot who just isn't going to stop in time).

I agree, I treat driving like a football game - if you don't want someone to tackle you, you need to know where all the other players are, all the time.

Whirlygig
13th Dec 2007, 21:28
I agree, I treat driving like a football game
Absolutely! How many penalties did you score? Personally, I prefer to rive like it's a scrum and one must know who ones flankers are! :}

Cheers

Whirls



oh sorry ... you meant soccer rather than rugby football!

stickandrudderman
13th Dec 2007, 23:15
I've never once heard of this in nearly thirty years over here.
I think you'll find, if you check out my web site (www.colinferns.com (http://www.colinferns.com)) that my experience probably trumps yours! (Although I could be wrong, it wouldn't be the first time!)

On two occasions in my driving life I have managed to spot in my rear view mirror a car heading towards my rear end, the driver having failed to notice that I've stopped. On both occasions I jumped on the gas and got out of the way, thus avoiding an accident. Do you think I should claim the amount of that driver's excess from him for avoiding an accident?

The notion that you shouldn't select park for fear of causing damage to the transmission in the event of a rear end shunt is a strange one. I accept that it's a remote possibility, but if the bloke who hits you has got to pay for the damage, does it matter?

In slow moving traffic I select nuetral and coast, rather than fight the car on the brakes. It saves the brakes and also saves a bit of effort!
(In my automatic car of course!)

As for brake light induced stress being a UK thing:
perhaps it's indicative of a general malaise amongst UK drivers?:O

Rollingthunder
14th Dec 2007, 00:20
We had a car with those little wing type things between the front and rear doors that popped out when the indicator stalk was used. They were not very bright and tended to freeze up in cold weather.

G-CPTN
14th Dec 2007, 00:35
those little wing type things between the front and rear doors that popped out when the indicator stalk was used.Called 'trafficators' and illuminated by a 'festoon' bulb (which had terminals at each end and a linear filament). The arm was raised by means of a solenoid which drew a metal rod into it by electromagnetism when energised.
http://www.morrisminor.uk.com/shop/images/lucas%20trafficator.jpg

SimWes
14th Dec 2007, 04:00
The wattage of a light bulb is dependant on the current drawn and the voltage applied.

Sorry to disagree, but the way I see it :}

P=IV (Power[watts]=Current[amps]*Voltage[Volts])

Wattage is set due to the type of bulb (21W etc) by the people who build them.
The only thing that should change is the current drawn. But then that only changes if you alter the Votlage

MadsDad
14th Dec 2007, 08:33
One other problem if you put an automatic into 'Park' at the lights is that when you do that (and when you move back to drive) it will go through reverse and the sight of the reversing lights coming on tends to raise the pulse rate of whoever is behind you (I did once have a mate who, when bored and sat in a traffic jam, often used to put his car into reverse and watch the panic behind him, to amuse himself).

Normally I'll hold on brakes if it's likely to be for a few (10 maybe) seconds, otherwise neutral/handbrake (in either manual or automatic).

frostbite
14th Dec 2007, 12:14
"In slow moving traffic I select nuetral and coast, rather than fight the car on the brakes. It saves the brakes and also saves a bit of effort!
(In my automatic car of course!)"


Doesn't your automatic car coast as a matter of course when you decelerate?

I wasn't prepared for this effect on my first auto drive and nearly lost it on a bend at the bottom of a hill.

matt_hooks
14th Dec 2007, 14:08
The current thinking on the use of engine braking is that, as modern braking systems are more than capable of locking the wheels, there is no need to use the engine to provide extra braking effort. This was not the case in many cars of old, so the use of the slowing effect of the engine/gearbox was useful in increasing available braking effort.
As G-C states, modern thinking is that brake linings are cheaper to replace than gearboxes, so the braking effort should come from those. You also have a more controllable system. I don't know many cars that have a completely smooth over-run curve, leading to a certain amount of lumpiness when slowing on the engine.
StickandRudder, "coasting" is not recommended as it means you don't have proper control of the vehicle. As you stated, it is often possible to lessen the impact of a rear-end shunt, or even avoid it completely, if you are alert and can move the car out of the way in time. If you are "coasting" then there is extra time to engage the correct gear, declutch and start moving, not there if you are already in gear. Of course if you are stopped temporarily, at traffic lights for example, then stopping the vehicle on the footbrake, putting the handbrake on and then taking the vehicle out of gear is recommended. I know people who go through clutches the way most people go through underwear, simply due to holding the vehicle on the clutch on inclines rather than using the handbrake and brakes as they are designed to be used. Again that's a generalisation, and there ARE times when I would slip the clutch, if only for a short period of time.
There are no hard and fast rules, the biggest rule is thinking what you are doing, and why, not just doing it because someone told you that was the best way.

<edited to add something germane to the post>

I think the whole indicator/brake light is, as stated above, to do with the different amount of the light absorbed by each colour of lense. I believe the amber, or orange indicators used in the uk allow a wider band of frequencies to pass, so a greater amount of light energy is passed through when compared to the red filters.

stickandrudderman
14th Dec 2007, 16:09
Perhaps instead of the word "coasting" I should have said "creeping".
(On the M4 in heavy traffic doing 5mph every morning!):ugh:

G-CPTN
14th Dec 2007, 16:50
I know people who go through clutches the way most people go through underwear, simply due to holding the vehicle on the clutch on inclinesDistinctly bad driving behaviour (and guaranteed to shorten the life of the clutch linings and possibly the pressure plate and maybe even the flywheel).
I have seen several engine flywheels where the surface was crazed with surface cracks (which again accelerates clutch lining wear) and the metal 'blued' due to excessive heat generated by slipping the clutch.
On the other hand, 'riding' the clutch (by keeping the transmission in gear with the clutch depressed) will accelerate wear of the release mechanism (probably some sort of bearing impinging on the release fingers of the pressure plate). Such behaviour can result in the bearing running hot and eventually becoming noisy or even inability to release the clutch (due to wear or collapse of the bearing and/or the release fingers - sometimes a diaphragm spring nowadays). In general, the clutch should only be used during gearchanges, and if the vehicle is stationary, then the transmission should be in neutral (although I agree that staying in gear in slow-moving traffic increases the ability to take avoiding action if necessary).

Most modern clutches should last for the life of the engine (I've had several 100,000 plus milers operating on the original clutch - but I don't do hill-holds or hill-starts with extra weight such as a loaded trailer).

Mexican overdrive - depressing the clutch on the downhill after climbing the hill in low ratio gear without disengaging the gear or upshifting. The transmission drive the clutch driven disc at speeds that far exceed the maximum engine speed, and the friction linings (now unrestrained by being clamped between the flywheel and the pressure plate) to centrifugal forces and part company with the retention (rivets or adhesive). In some design of 'pot' flywheel (where the clutch sits in a recess) this will jam the clutch assembly so that disengaging the clutch isn't possible. Getting the driver to admit their action can be interesting - they will argue that they never did ride the clutch whilst the vehicle coasted downhill at high speed whilst still in low ratio gear, but the evidence is irrefutable . . .

Providing you can get a vehicle moving, it is possible to drive (and change gear) without use of the clutch (for example if the clutch cable breaks) - provided you can synchronise the engine revs accordingly by applying or releasing the accelerator. It's not very kind on the gearbox synchromesh (if it has any) or on the gear-engagement dogs, but in an emergency it IS possible. Start the engine with bottom gear engaged (and the brakes released) and then progress up and down through the gears as necessary. Once drove over 100 miles with a snapped clutch cable (including onto and off the North Sea Ferry).
Of course you can trash the gearbox if you don't understand what you are doing . . .

Out Of Trim
14th Dec 2007, 17:27
Providing you can get a vehicle moving, it is possible to drive (and change gear) without use of the clutch (for example if the clutch cable breaks) - provided you can synchronise the engine revs accordingly by applying or releasing the accelerator. It's not very kind on the gearbox synchromesh (if it has any) or on the gear-engagement dogs, but in an emergency it IS possible. Start the engine with bottom gear engaged (and the brakes released) and then progress up and down through the gears as necessary. Once drove over 100 miles with a snapped clutch cable (including onto and off the North Sea Ferry).
Of course you can trash the gearbox if you don't understand what you are doing . . .

Yes, I used to own an old Audi Coupe - Had it for about 14 years; It had a very heavy clutch even with a new clutch, release bearing and cable fitted. I must have got through about six or seven clutch cables in that time and became quite adept at driving without a clutch! And indeed with changing said cable myself. (Not that easy on that car! - later models had a hydraulic clutch instead.) Traffic jams were a nightmare; one's left thigh muscles would eventually go into spasm with the amount of effort required in stop/go traffic.

On the last occasion it wasn't the cable that went but indeed a part of the whole clutch pedal broke-off which of course had the same effect. I was about halfway home from work and restarted the car in gear and drove on home, and then again onward to a garage in Haywards Heath for repairs. It was an interesting journey to say the least; especially approaching roundabouts on dual carriageways and pedestrian crossings, traffic lights etc.

Also had to reverse into the driveway at my parents house without a clutch once at about 1am - don't know how I did it really as there wasn't much room for error and parking alongside my Dad's car :eek:(eek!), but didn't have enough strength to push it up the slope on my own.

Peter Fanelli
14th Dec 2007, 19:23
The wattage of a light bulb is dependant on the current drawn and the voltage applied.

Sorry to disagree, but the way I see it :}

P=IV (Power[watts]=Current[amps]*Voltage[Volts])

Wattage is set due to the type of bulb (21W etc) by the people who build them.
The only thing that should change is the current drawn. But then that only changes if you alter the Votlage



Seems to me what you said and what I said are the bloody same.

"the wattage of a light bulb" (P) = "current drawn" (I) x Voltage Applied (V)

What happens if you add a couple of volts, is the light bulb still 21 watts?

west lakes
14th Dec 2007, 19:47
The rating of the bulb is more correctly stated as 21W at 12V.

The only constant factor is the resistance of the bulb R (Ohms)

If you look at ohms law where I = V/R
Add that into the power equation P = V x I
Then P = V x V/R
Or P = V2/R

So yes as the voltage increases the power increases & vica versa.
The only time you are going to get approx 12V is when the engine is not running, with it running voltage increases because of the alternator and can be anywhere between 12 and about 14 dependant upon the electrical load of the car.
Conversly if the alternator fails and as the battery gets discharged the Power will reduce which is why the lights get dimmer. Or if you leave your lights on when you switch the engine off.

ZFT
14th Dec 2007, 21:38
West Lakes,

Not strictly correct. When a filament is heated its resistance increases thus the current decreases and the light output will decrease.

SimWes
14th Dec 2007, 23:08
Well that's me bloody well told then...:\
Any hoo,
At 12V it draws 21W
At 10V it draws 15W ish
At 14V it draws 28W ish

G-CPTN
14th Dec 2007, 23:16
When a filament is heated its resistance increases thus the current decreases and the light output will decrease.until the increase in voltage causes the element to melt, whereupon the light emitted briefly increases before it ceases permanently.

ShyTorque
14th Dec 2007, 23:26
Stick and Rudder,
The notion that you shouldn't select park for fear of causing damage to the transmission in the event of a rear end shunt is a strange one. I accept that it's a remote possibility, but if the bloke who hits you has got to pay for the damage, does it matter?
In slow moving traffic I select nuetral and coast, rather than fight the car on the brakes. It saves the brakes and also saves a bit of effort!
(In my automatic car of course!)

Why "a strange one"? Because you haven't considered it? If some gimp damages my rear bumper, I can still get to my destination. If my transmission's damaged, my inconvenience will be much worse. I just see that as common sense. Better in my book to prevent big damage than to rely on a big insurance damage claim....

My car also has to go through "R" to go to and from "P" and "D"; and there is a slight delay in the shift, causing both the reverse lights AND the brake lights to come on. I thought the intent was to minimise the unecessary illumination of rear facing lights?

If I put my auto box in neutral and coast at slow "traffic jam" speed, the interlock prevents me going back into "D" unless I apply the brakes quite positively, just as if I had stopped and want to set off again, as I mentioned in the previous post. I could cause a rear-end shunt accident doing that; braking for no apparent reason at a time when the traffic ahead of me is accelerating.

Maybe when driving you should just wear some cool shades and chill out a little? :cool:

frostbite
15th Dec 2007, 12:12
Look, this voltage/wattage theory is all very well, but ani fule no that it all depends on how hard you press the brake pedal.

The harder you brake, the more volts are forced down the wires and if you brake too hard the smoke capsule will burst and fill the bulb which won't work any more.

G-CPTN
15th Dec 2007, 12:22
In days gone by that would, indeed, be partially true, frostie. My 1938 MG had a mechanical brake-light switch which operated by pulling on a spring which moved a bar which touched two contacts. Partial brake application would result it a 'twittering' response with weak or intermittent illumination of the brake lamps, whilst a full-blooded panic stop caused the spring to effect it's maximum force, thus ensuring full current flow (and maximum brightness of the bulbs).

At lower application rates the resistance of the partial contact within the switch would effectively reduce the voltage across the bulbs, with 'full' voltage (or as close as possible) would occur once the switch contacts 'shorted-out'.