Brake Light / Regen question

Brake Light / Regen question

I don't know if this is worthy of an entirely new forum topic, but can anyone tell me whether the brake lights come on when you are regen braking in the Model S? Driving in to work this morning in the rain with low visibility it occurred to me that it might be good for the guy behind you to know you're slowing down, even if you haven't necessarily stepped on the brake pedal...

archibaldcrane | September 17, 2012

From what I've read, your brake lights will come on if the regenerative engine braking slows your car down beyond a certain rate, so yes.

BYT | September 17, 2012

Yes, this was brought up on many test drives and was confirmed based on g-force if I remember correctly.

More info or a thread on this here:

Electric Machete | September 17, 2012

Telsa uses an accelerometer to determine when to apply the brake lights.

up4air | October 6, 2012

I'm seeing Tesla sedans on the road in Menlo Park and followed one on my way home yesterday. I noticed that the brake lights came on often and I thought needlessly. It looked as if the driver was two foot driving and feathering the brake pedal. Then it occurred to me that the regenerative braking could be culprit.

Having regenerative braking turn the brake lights on is strange (to me). Drivers used to downshifting will find this counter intuitive and annoying when you're following.

Can the accelerometer's sensitivity vis-a-vis braking be software controlled or turned off?

I would also like to see a more aggressive regenerative brake, something closer to lifting off the gas with a manual transmission.

Michael23 | October 6, 2012

Yeah you'll look like you are brake pedal happy for sure in this car, but at least when the car behind you brakes in reaponse you can gun it to get away quicker.

BYT | October 6, 2012

What I will love is the impatient person behind me assuming I'm a slow ride the brake driver until they mistakenly try to pass me! ;)

dahtye | October 6, 2012

I noticed in a recent video (might have been Car and Driver review) that the brake light looked yellow or amber. Did anyone else notice that on the video and if this is the case, does anyone know whether this is the regen braking color? Or maybe this was an optical illusion due to lighting during the video? I don't think yellow would be an approved actual braking color (from an NHTSA standpoint).

sergiyz | October 6, 2012

They are red, it's a video artifact.

Volker.Berlin | October 8, 2012

I noticed the same. It's here, and yes, it seems to be just blown-out red:

And here:

And here's the blinker, which presumably is the same light:

Finally, here it becomes clear that the brake lights are actually bright red and not yellow:

cliffordbaynon | February 12, 2015

I am shopping my 1st Model S now, and have a

Isn't coasting a natural part of driving in mild traffic conditions?
To be only ACCELERATING or BRAKING seems like you have lost something in the natural flow of how most of us drive.
Also the constant brake light going on for the poor soul following you every time you don't want to slow down, but simply no longer want to accelerate seems extreme.

I am aware that the regenerative braking can be turned off, but any insight on this issue appreciated.

-Future Model S owner

Bighorn | February 12, 2015

asked and answered the other place you cut and pasted this question

Captain_Zap | February 12, 2015

"Coasting" is not a natural part of driving unless there is a hill involved.

Artificial propulsion is a vestigial artifact from ICE engines and automatic transmissions that had to engineer in efficiencies for MPG goals.

It is nice to be set free from that limitation. That is one reason I was driving cars that either had a manual transmission or performance cars that 15 to 20 years old with sportier gearing. The fake propulsion made me crazy. If I don't provide fuel to the car, it shouldn't go anywhere unless gravity is involved.

Tesla added creep for those that grew accustomed to that ICE propulsion artifact, but comes with at a cost to efficiency in an EV.

Haggy | February 12, 2015

"Coasting" is not a natural part of driving unless there is a hill involved.

If you are driving on a crowded freeway and traffic ahead slows down, you can take your foot off the accelerator of an ICE vehicle and either maintain your distance or reestablish your distance after getting a bit closer initially. The alternative is to get closer and then use the brakes, which causes cars behind you to do the same and that increases congestion. Using your brakes on a freeway shouldn't be a natural part of driving. Ideally it should be for sudden, rare unanticipated events. Unfortunately there are so many bad drivers that it's rare that I can make a trip in the Bay Area without ever using my brake pedal in an ICE car, but you'd be surprised at how rarely it's needed if you control your speed. Many people are used to controlling their speed by taking their foot off the accelerator when traffic slows down ahead. With a safe following distance, brakes shouldn't be needed for typical variations in speed.

paul | February 12, 2015

@cliffordbaynon - a small change in habit is all that is required. The pedal on the right is no longer solely a "go faster" pedal, it's also a "go slower" one. If you want to gain a similar effect to coasting (not sure why you would) you simply don't take your foot all the way off the pedal.

This can be visualised on the dash by having the power level neither in the orange nor the green - just at 0.


rhbohl | February 12, 2015

I would like to see an indicator on the dash when the brake lights come on, so as to help manage giving potentially confusing information to a following driver.

hammer @OR-US | February 12, 2015

@clifford I found during my test drive I adjusted immediately to the new style. When we stopped to exchange drivers at the halfway point I remarked to the sales advisor that I hardly touched the brake. My wife took a little longer to get used to it but by the time we got back to the store she had it down. Not an issue, very easy to modulate.

Haggy | February 12, 2015

Those situations where you would want to coast to reestablish your distance could also be handled by using TACC. Those with older vehicles are already used to the idea of driving a certain way. It takes a little getting used to.

Pressing the battery icon will give a window that shows the status of brake lights and much more. It's perhaps less ideal than seeing it on the dash, but once you do it a few times you will have a good enough idea that you won't need to see it. It's more of a peace of mind thing to let you know that the car is really putting on the brake lights when it should. In my experience, it will actually be using the brake lights far more than you might have used them had you coasted to slow down.

steinmail | October 7, 2015

I agree with rhbohl. A "brake light on" indicator in the dashboard would be very helpful. It might train us to drive with slighter variations in "gas" pedal pressure and thereby make us better drivers.

DTsea | October 7, 2015

No idiot lights.

No need.

No problems. No reports of rear ending.


mrspaghetti | October 7, 2015

Holy ancient thread resurrecting Batman! I think this must be my first post, getting teary...

ColonyGolfer | October 7, 2015


1. Wait until dark
2. Drive down the road with regen activated
3. Activate the rearview camera
4. Remove your foot from the accelerator

You will see a red glow in the rearview screen caused by your brake lights.

sule | October 7, 2015

Regen is not tied to brake lights. Deceleration is. I haven't tested this thoroughly but Tesla official said that this is based on accelerometer measurements and it is regulated for new cars. We had a debate on this before, here, but don't remember the end of it.

Essentially, if you find a steep hill and go down with strong regen but not enough to decelerate beyond that threshold the brake lights should not light up.

Points to take home:

1. You drive as you should DRIVE, not to have a better light show. Light are there for a reason.

2. This is regulated. It must do what it does.

3. Any indicators beyond super obvious ones would draw attention away from driving. Remind yourself of point (1) here, again. Super obvious indicators would be both super distracting and super ugly.

4. Indicators are not needed.

5. You don't need to know what the brake lights are doing as long as they are, indeed, doing what they should.

Other than that, accelerometer is just another component that could, in rare cases, go beserk. But, then again, so could other things in other ways. This would need to be checked.

EVino | October 7, 2015

When brake lights come on is one of those mysteries that seem to not have a definitive precise answer. We have it on faith that it happens during regen, based on some accelerometer load. I know it works, but I'm not precisely sure when it turns on. I don't think anyone else knows, short of seeing the screen, precisely when the brake light will turn on. I agree that an indicator light (one we can really see, not the dim one on the touchscreen) would be helpful because it can reinforce our sensory memory. Over time one will get a feel for it, but sensory training can't occur without feedback. Think back when you drove a manual transmission car. The sound of the engine was the telltale when to shift. You got a feel for the rpm, because the sound was the feedback. EVs are silent and the downside can be the lack of feedback regarding speed, load, acceleration, or deceleration. Haptic, audio, or light signals would help give back some artificial mechanical feel to this digital car. I believe the Model X has an indicator which reflects when the brakes come on.

trixiew | October 7, 2015

Mrs Paghetti you look so young!

brec | October 7, 2015

If the 7.0 software beta shown in this video reflects what will actually be delivered, those who want brake light indication on the instrument panel will be pleased:

mrspaghetti | October 8, 2015


Thanks, I try to eat right and exercise my fingers so that my typed words maintain their toned, youthful appearance.

But I am actually Mr. Spaghetti, unless and until I decide to go the Bruce/Caitlyn Jenner route. And given the results of that, it's looking unlikely.

sbeggs | October 8, 2015

Is it possible to flirt with someone if you don't know their sex?

mrspaghetti | October 8, 2015


Would you care to discuss it over sushi?

[I believe this answers your question, btw]

Bighorn | October 8, 2015

As they like to note in college now, gender is not a binary.

trixiew | October 8, 2015

the new term is "gender fluid".

Bighorn | October 8, 2015

Sounds like it stains. | October 8, 2015

And, genderally speaking, the brake light does turn on when you take your foot off the accelerator, unless your battery pack is very full or your car is very cold.

Larry@SoCal | October 8, 2015

Press the"T" on the UI. You will see that the light does not come on with gentle regen. You will see that it comes on with harder regen or with the brake pedal.
You will find that it is very natural and correct and you will soon tire of monitoring it.

David Trushin | October 8, 2015

Tesla has included a dwim relay into the brake circuitry. It determines if you would have put on the brakes were you driving an ICE and acts accordingly. Smart people, those Teslas.

EVino | October 8, 2015

My argument for having an indicator is to be able to associate your sensory memory to the braking behavior of the car. No one knows precisely when the brake lights go on. We know it works, but not the precise moment when. In ICE cars we have certainty because you know when your foot is on the brake. The indicator can be ignored if comfortable.

J.T. | October 8, 2015

@Larry Pretty sure the "T" doesn't work anymore. You need to go to the charging screen, but 7.0 will make the whole problem moot.

MichaelN | October 8, 2015

Hit the battery Icon - drive the car and watch the tailights on the screen - in that mode the lights are displayed and lets you know they are working and when --

EVino | October 8, 2015

Not good enough. It's out of field of view, very dim, and negates use of other screen functions.

DTsea | October 8, 2015

Evino, just drive. It doesnt matter to know when the lights come on. Just a distraction.

EVino | October 8, 2015

I know, I get it. I just get overly aware that I'm not being a jerk to the car behind me when my brake lights keep flashing on because of regen braking. If I knew just when that point is, I think it will improve my "feel" for the throttle control. I'm the kind of driver who likes to row gears in a manual car and I love that same downshift response of regen, just not the schizophrenic brake lights.

David Trushin | October 8, 2015

Whenever i drove in a standard shift car and engine braked, i worried about getting rear ended because the brake lights wouldn't go on. Now i don't worry about the car in back. If the driver is annoyed it's their problem. If he's sitting in my back seat, then it's mine.

mrspaghetti | October 8, 2015

I've found myself behind Teslas a couple times in traffic and I didn't notice that they flashed their brake lights abnormally at all.

PBEndo | October 8, 2015

There are a few videos of Teslas on dunks with their brake lights illuminating as the wheels are slowing down after a test. During the slow down the driver should not be pressing the brake pedal and there is no acceleration of the car. This may indicate that there is an additional speed trigger for the lights.

PBEndo | October 8, 2015

Dunks = dynos