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Discussion Starter · #1 ·
In my town the accident I’m most worried about is some distracted driver rear-ending me. Given that I use one pedal driving almost exclusively and that the braking effect is so pronounced, especially at low speeds, does anyone know at what threshold the rear brake lights are activated during OPD? Should I be more concerned about this than if I used the friction brakes more often?
 

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I asked about this during my test drive and was told it was related to a certain measure of Gs - but I can't remember what it was. My wife followed me on a 25 mile trip last Saturday and I exclusively used OPD (apart from one point where a truck pulled out on me) and she said she only saw my brake lights come on twice I think (there were a number of roundabouts so I did have to slow down).
 

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Weirdly I was thinking this literally 5 mins ago as I drove my car for its first proper journey...might do some experiments in the dark when I should see them in my mirrors
 

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Yes, it's related to the legal deceleration limit, and also flashes 4 times if you use maximum braking force. It's all in the manual, folks!

Edit: links to the relevant sections in the manual:
 

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I have wondered over this too. I don't know the answer. What I do know is when you come to a stop and take your foot off the brake (creep off), the brake lights stay on. I can tell by the driver behind being lit up red. I wish it didn't do this, as it's my pet hate when people sit with their foot on the brake shining bright red lights in the driver's eyes behind.
Started using park more since I realised.
 

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I asked about this during my test drive and was told it was related to a certain measure of Gs - but I can't remember what it was. My wife followed me on a 25 mile trip last Saturday and I exclusively used OPD (apart from one point where a truck pulled out on me) and she said she only saw my brake lights come on twice I think (there were a number of roundabouts so I did have to slow down).
Yes I asked too - As I recall 0.6g by my basic maths a deceleration of >13mph per second (apologies to the units police 👮‍♀️) my feeling was this was not a sensitive enough deceleration to trigger lights which appears to tie in with smithers197 experience. So you could slow from 30mph to stop in 5 seconds using regenerative braking and not trigger the brake light! I would be interested to confirm that figure with Polestar.
 

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Discussion Starter · #9 ·
Yes, it's related to the legal deceleration limit, and also flashes 4 times if you use maximum braking force. It's all in the manual, folks!

Edit: links to the relevant sections in the manual:
The brake light also comes on during regenerative braking if the braking force exceeds a certain level.
This is where the manual is supremely unhelpful, and why I’ve learned a lot more from this forum than from reading the manual (which I’ve done all the way through on one occasion).
 

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#if the braking force exceeds a certain level.

Your Polestar activates the brake lights like every other car at a decelaration level which is requested by the regulations.
Even the newer petrol cars have it this way: activated by the level of decelaration.
Only on older cars it is activated mechanically by the pedal.
 

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Discussion Starter · #11 ·
I guess what I’m really asking then is, “Does anyone have a sense of how often, in practice, the brake lights come on during standard OPD?”
 

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More than when using ICE engine braking. If you are concerned then don't use OPD.

The flip side would be every time you lift off slightly the brake lights come on. That would be even more annoying.

If I am driving on a motorway in an ICE or the EV coasting and I am just slowing slightly and following cars are hundreds of meters away (but closing) then I would lightly brush the brake pedal to flash the brake lights as a warning.
 

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I had this exact same question!

#if the braking force exceeds a certain level.

Your Polestar activates the brake lights like every other car at a decelaration level which is requested by the regulations.
Even the newer petrol cars have it this way: activated by the level of decelaration.
Only on older cars it is activated mechanically by the pedal.
In the US they're required to be activated when the "service brakes" are activated, so they have to be tied to the pedal.

As far as OPD, the NHTSA reg is kinda... vague:
For an EV equipped with RBS, the RBS is considered to be part of the service brake system if it is automatically activated by an application of the service brake control, if there is no means provided for the driver to disconnect or otherwise deactivate it, and if it is activated in all transmission positions, including neutral.
For the P*2, the car uses regen when the brake pedal is depressed up to a certain threshold, so that makes it part of the service brake system. What's unclear is if mere lift-off counts as "application of the service brake control." The car uses the friction brakes below a certain speed, so... I dunno.

P.S. NHTSA also says the lights: "May also be activated by a device designed to retard the motion of the vehicle."
 
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The P*2 seems to use a different decelleration threshold than the VW e-UP! based on my experience and tests. Even medium-light decelleration due to slight liftoff is signalled with brake lights in the VW.
 

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There's going to be a spike in whiplash cases as P*2 drivers trigger emergency braking because they were staring in their rear views to see if the brake lights illuminate.

In Europe we have the following regulation:
  • decelaration below 0,7 m/s2 - no brake light
  • decelaration between 0,7 m/s2 and 1,3 m/s2 - it is up to the car manufacturer
  • decelaration above 1,3 m/s2 - the brake lights must be on
in modern cars like Polestar this is done by the electronics

Source:
https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2018/R013hr4e.pdf
Ok, for clarity, any manual activation of the brake system will trigger the lamps. From that same doc:
Activation of the service braking system by the driver shall generate a signal that will be used to illuminate the stop lamps.
It's essentially the same as the US, but it has guidelines for when automatic systems or regen illuminate the lamps. I'll poke around the NHTSA some more and see if it's buried in an addendum.
 
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I guess i'm just too trusting and assumed all was well and the lights just worked until I read this thread. So last night I tried it out in the dark and the brake lights definitely come on when I lift my foot off or nearly off the pedal. Hence more or less what PisontCrack outlined in his post. I assume it's not just my car that does this but all of them.
 

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I guess i'm just too trusting and assumed all was well and the lights just worked until I read this thread. So last night I tried it out in the dark and the brake lights definitely come on when I lift my foot off or nearly off the pedal. Hence more or less what PisontCrack outlined in his post. I assume it's not just my car that does this but all of them.
No question on if they turn on or not, was more around when.

Seems there's also an acceleration threshold for turning them off too.
 

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Seems like the assistant at my test drive might have meant 0.6m/s/s rather than 0.6 g!
I asked about this during my test drive and was told it was related to a certain measure of Gs - but I can't remember what it was. My wife followed me on a 25 mile trip last Saturday and I exclusively used OPD (apart from one point where a truck pulled out on me) and she said she only saw my brake lights come on twice I think (there were a number of roundabouts so I did have to slow down).
Yes I asked too - As I recall 0.6g by my basic maths a deceleration of >13mph per second (apologies to the units police 👮‍♀️) my feeling was this was not a sensitive enough deceleration to trigger lights which appears to tie in with smithers197 experience. So you could slow from 30mph to stop in 5 seconds using regenerative braking and not trigger the brake light! I would be interested to confirm that figure with Polestar.
 
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