[Farnalien]

My scientific mind is really bugging me about this.

We know the behaviour of a Tesla's brake lights does not exactly match those of an ICE vehicle with an automatic transmission. Does this confuse non EV drivers who follow? Is this a factor in the frequency of rear end collisions?

In an ICE, a "medium" deceleration rate requires that the brake pedal be depressed, which in turn displays the brake lights. However, for a similar regeneration deceleration rate of a Tesla, the invocation of the brake light display is determined by a computer which may take into account several factors, including the vehicle's deceleration rate. Theoretically, the computer activation of the brake lights could be initiated sooner as the distance to the following vehicle decreases.

An experiment could be performed, resulting in a graph of deceleration rates versus the invocation of brake lights for both an ICE with automatic transmission and a Tesla with full regeneration and partial regeneration. (Hey @TrevP , would you know of anyone that might want to do a video?)

If the car's instrument display were improved to show an easily noticeable large red glow around the brake lights when the brake lights are lit rather than the barely detectable indicators (especially problematic with red cars) we have today, Tesla drivers would receive solidly reliable feedback and have full confidence that the brake lights are on or off. This would allow the drivers to decide whether they should (slightly) depress the brake pedal earlier to ensure the brake lights are on to further protect the vehicle from rear end collisions and tailgaters.

Brian
Model 3, Long range, Dual Motor, Silver metallic, 19" sport rims, 19" Replika R241 winter rims

 

[JCE]

I have followed my wife’s Model 3 on many occasions and not once did I think the brake lights had a weird pattern to them. It just looked “normal” for lack of a better term.

I can understand the question to “does my break light turn on when I have regenerative breaking” but this obsession with whether the light comes on or off or how or even considering driving different control the breaks lights seems a bit crazy.

 

[jdcollins5]

+1 - My wife has followed me many times and said the brake lights worked just like any other car. Nothing unusual.

 

[JasonF]

In heavy stop-and-go traffic I'm sure the brake lights come on earlier, because they come on as soon as you let off the accelerator, before you go to the brake. That sounds safer to me.

Also, look at the white "ground" behind the animated Model 3, you'll see a red cast from the brake lights when they're lit. It's easier to see than the tiny lights.

 

[MelindaV]

In heavy stop-and-go traffic I'm sure the brake lights come on earlier, because they come on as soon as you let off the accelerator, before you go to the brake. That sounds safer to me.

Also, look at the white "ground" behind the animated Model 3, you'll see a red cast from the brake lights when they're lit. It's easier to see than the tiny lights.

Or if your tint installer attempted to wipe the water drips from the 3rd brake light area, you can see the light seep in the rear view mirror where the foam was torn 🤨

 

[Farnalien]

One applicable scenario is in bumper to bumper traffic when trying to maximize the car's efficiency by monitoring the traffic ahead and minimizing the car's changes in speed (acceleration/deceleration). In many cases, the car will decelerate with partial regen faster than that of an ICE car's coasting deceleration rate with only small changes to the position of the accelerator pedal, such that the right foot remains on the accelerator pedal, and without the brake lights coming on. In my ICE car, I would have had to press the brake pedal (with the brake lights coming on) to slow the car down below its normal coasting deceleration rate and to match the equivalent deceleration rate of the partial regen in the Tesla. Any thoughts?

 

[MelindaV]

One applicable scenario is in bumper to bumper traffic when trying to maximize the car's efficiency by monitoring the traffic ahead and minimizing the car's changes in speed (acceleration/deceleration). In many cases, the car will decelerate with partial regen faster than that of an ICE car's coasting deceleration rate with only small changes to the position of the accelerator pedal, such that the right foot remains on the accelerator pedal, and without the brake lights coming on. In my ICE car, I would have had to press the brake pedal (with the brake lights coming on) to slow the car down below its normal coasting deceleration rate and to match the equivalent deceleration rate of the partial regen in the Tesla. Any thoughts?

I am in stop and go bumper to bumper traffic for near 2 hours a day, and can tell you the brake lights come on at least as often as the cars I am around, if not more often

 

[Farnalien]

I am in stop and go bumper to bumper traffic for near 2 hours a day, and can tell you the brake lights come on at least as often as the cars I am around, if not more often

Thanks, that is somewhat comforting to know. I forgot to mention that as my car doesn't have Autopilot, I always need to manage its speed myself.

 

[gary in NY]

I've watched my display (when possible - usually after sundown) to get a better idea about when the lights are triggered by regen. After a few times, you get a feel for the trigger point. Why do this? Who knows, but I was curious. Mainly, I thought it might look weird to other drivers if the lights came on when using heavy regen at highway speeds (they will come on when the car slows quickly-just like hitting the brake). The brake light algorithm takes many factors into account, including your traveling speed and the amount or regen applied, and the results mirror the average human ICE driver response in the same circumstances.

What may look weird to other drivers is coming to a stop under light regen, not hitting the brake, and stopping. No brake lights at all (creep is off). I do this quite often, and will hit the brake if someone comes up behind me, else they may think I'm moving. Feels like a manual transmission in neutral in this case.

 

[Farnalien]

What may look weird to other drivers is coming to a stop under light regen, not hitting the brake, and stopping. No brake lights at all (creep is off). I do this quite often, and will hit the brake if someone comes up behind me, else they may think I'm moving. Feels like a manual transmission in neutral in this case.

Yes, and with the latest update providing regen until the vehicle is stopped, placing itself in "hold", it should be relatively simple to detect if and when the brake lights come on under light regen. Has anyone tried this scenario with the latest update?

 

[SoFlaModel3]

To be honest this never crossed my mind. Perhaps because I used to drive manual transmission cars and loved rowing through the gears to slow the car without ever using the brakes.

 

[Farnalien]

To be honest this never crossed my mind. Perhaps because I used to drive manual transmission cars and loved rowing through the gears to slow the car without ever using the brakes.

Yes, absolutely right. While stopped as the lead car at a traffic light in <Hold> mode with <Creep> off, I sometimes release and depress the brake pedal again to disable <Hold> mode (the <Hold> indicator changes to the numeral zero) and then release the brake pedal. This is analogous to a manual transmission car with the clutch pedal depressed and with the brake pedal released. As the car is not in <Hold> mode and the brake pedal is not depressed, the brake lights are not on and the guy behind me is wondering why my car isn't moving forward. Of course, if I'm on a hill, the car would begin to roll either forward or backward downhill.

 

[msjulie]

I for one would prefer a better indication - this is the first car I've owned that is not a manual trans and I was keening aware that engine braking was not giving the folks behind me good indication I was slowing. Sometimes it would be prudent for me to lightly apply the brake pedal to give them the feedback they required to be properly attentive (sounds like brake checking them but I make a huge effort not to though it has happened I've had to on/off the brakes to get them flashing so the person looking down at their phone behind me wakes up)

In the Tesla, since you can modulate the car's speed so well with just the throttle and often never trigger the brake lights (they don't just come on with your foot off the throttle but based on deceleration rate) I find I want to know if they are on - it's much harder to get someone's attention I find, or maybe folks are just less and less attentive.. to get the on/off light behavior in this car is harder if you don't know if they are already on and light brake pedal application isn't adding anything..

My car being red makes it the brake lights in the on-screen car just that much less obvious

 

[Farnalien]

In the Tesla, since you can modulate the car's speed so well with just the throttle and often never trigger the brake lights (they don't just come on with your foot off the throttle but based on deceleration rate) I find I want to know if they are on - it's much harder to get someone's attention I find, or maybe folks are just less and less attentive.. to get the on/off light behavior in this car is harder if you don't know if they are already on and light brake pedal application isn't adding anything..

Yes, with regen braking, the car behaves as a blend of manual transmission and automatic transmission vehicles with <Creep> mode and the amount of regen being behaviour modifying factors. Those of us who have driven manual transmission vehicles with the deceleration of engine braking (analogous to that of regen braking) are likely more cognizant of the on/off state of the brake lights since it is necessary to accurately communicate one's intent to the surrounding drivers.

 

[gary in NY]

The other thing that the car does that really is odd, and potentially dangerous in specific circumstances, is the tail light behavior when stopped. I can stop the car, brake on hold, put it in park, get out to check the mail, and the tail lights go off while the headlights stay on. Park cancels the brake lights, but the tail lights also go off, unlike any other car I've owned. Dangerous in my situation because I'm on a somewhat blind curve on a very dark road. 30 seconds is all I need, and I've always wondered why they don't remain on with the headlights. Can't use that much energy in that short amount of time. Not a brake light problem per se.

 

[Farnalien]

Park cancels the brake lights, but the tail lights also go off, unlike any other car I've owned.

I've wondered about that. I've observed my headlights being on in bright daylight as I arrive at the driveway of my house. It could be related to the car automatically opening the garage door. I'll have to pay more attention and check whether the taillights are always in sync with the headlights.

 

[MelindaV]

The other thing that the car does that really is odd, and potentially dangerous in specific circumstances, is the tail light behavior when stopped. I can stop the car, brake on hold, put it in park, get out to check the mail, and the tail lights go off while the headlights stay on. Park cancels the brake lights, but the tail lights also go off, unlike any other car I've owned. Dangerous in my situation because I'm on a somewhat blind curve on a very dark road. 30 seconds is all I need, and I've always wondered why they don't remain on with the headlights. Can't use that much energy in that short amount of time. Not a brake light problem per se.

have you emailed Tesla?
[email protected]

 

[gary in NY]

have you emailed Tesla?
[email protected]

No I have not. Didn't think of doing that. Thank you.

 

[Love]

No I have not. Didn't think of doing that. Thank you.

By chance would the option to leave the headlights on have any impact at all on this? I've seen that option within the menus but have it selected to off. I know it sounds silly as it clearly states "headlights" but maybe it also keeps the taillights on for 30 seconds?

 

[victor]

The other thing that the car does that really is odd, and potentially dangerous in specific circumstances, is the tail light behavior when stopped. I can stop the car, brake on hold, put it in park, get out to check the mail, and the tail lights go off while the headlights stay on. Park cancels the brake lights, but the tail lights also go off, unlike any other car I've owned. Dangerous in my situation because I'm on a somewhat blind curve on a very dark road. 30 seconds is all I need, and I've always wondered why they don't remain on with the headlights. Can't use that much energy in that short amount of time. Not a brake light problem per se.

If it's "dangerous in my situation because I'm on a somewhat blind curve on a very dark road" then just use Hazard Warning Flashers. Just press a button above you before exiting the car and press one more time when you're back.