This is a common question, yes the brake lights are activated when the vehicle slows. Common belief is that past a certain braking rate / g-force the brake lights are activated, whether decelerating by lifting foot off the accelerator in Low and/or using the RoD paddle. If you're a Bolt owner, watch in your rear-view while in traffic, if there's a truck behind you with a chrome grille you can see the lights activating as you slow. Try not to have a crash in the process though!

 

you can also see the reflection from the center brake light reflecting off of the windshield wiper at night. just look in your rear view mirror.

 

I can confirm that in general when you take your foot off the gas in low the lights come on. If you sitting at the a light and the car is stopped without your foot on the brake I'm pretty sure the brake lights are NOT on. I usually pump the pedal if someone is coming up begind me in this situation....but then again I was rear ended in my Volt in low....

Madmike

 

i tested this today:

- in D, regen/brake lever behind steering wheel is held to stop, brake lights come on, but when fully stopped, there are no brake lights
- in L, slowing down, brake lights come on, but when fully stopped, there are no brake lights
- only way to have brake lights on when fully stopped is to use the brake pedal

i'm not a fan of the way this works to be honest. it's unsafe sitting at a red light with no brake lights on when you're in L/one foot mode

 

i'm not a fan of the way this works to be honest. it's unsafe sitting at a red light with no brake lights on when you're in L/one foot mode

I argue it is unsafe to be stopped without your foot firmly on the brake pedal or setting the parking brake. If the car is hit from behind, it will move a lot farther if the friction brakes are not firmly applied. This could move the car into the intersection when it could be hit by cross traffic.

Even if the brake lights stayed on when stopped in "L" mode, I equate remaining stopped without firmly pressing the brake pedal to turning the wheels to the left while stopped making a left turn. It is asking for trouble that could be avoided.

It is not very difficult to press the break pedal. Why risk the consequences of not doing it?

 

Someone said that it depends on the G force that it takes to slow the vehicle.

Can someone TELL ME WHERE on the dash it states the 'g' force? I have not been able to see this anywhere. Is it in a specific place?
Maybe someone can show me with a picture.

I have played with the L mode and that is what I drive in all the time. If i really just let off the pedal Brake lights come on. I do feather off it and know it doesn't come on much that way, so I let off faster if someone is behind me.
Then again I pay VERY close attention to all drivers near me. If they are not really paying attention I kinda BRAKE them and they notice me a bit more

 

there is no driver-facing display of the deceleration force, it's all internal. i believe someone used a handheld meter to measure it.

 

Many phones and tablets have accelerometers built in, install an app that uses it and measure stopping g-force that way.

 

I think the "smart people at GM" probably figured out what a good difference between coasting and slowing down means in terms of deceleration (and hence G-force) which turns on the lights. If you are slowing down so gradually that your brake lights don't come on, the driver behind probably isn't going to rear end you because you really aren't slowing down very quickly.

In reality, this is all very situational. Try driving up a steep hill, in any car in drive, take your foot off the gas - you will slow very quickly, but you won't see any brake lights! Does this suddenly mean that the brake light system in all cars is unsafe?

Probably the best way that break lights could be implemented would be to monitor for a speed delta and if the speed delta over a certain period of time reaches a threshold, the lights come on. If speed drops to 1 or 2 mph or lower, break lights are always on. Why is it even tied to the brake pedal at all really?

 

Great, I thought I was missing something as someone said it was on the DIC.
I'm good not about to download a silly program when it really isn't necessary. Too much crap to look at now while driving that anything else is distracting.

 

What I found looking at the reflection off the road reflectors behind me is that the brake light turns on based on the degree of your deceleration, namely only at the end of your stroke, that is full L mode (foot nearly off the pedal or off the pedal). It occurs before you take your foot off, maybe around the 90% mark.

Seems like a good design decision, just pulling back when in L is equivalent to transmission braking in a car, more or less. You may or may not come to a full stop in this case. However going full L (or nearly) will bring you to a stop, so brake light is appropriate.

If you want to engage the light just use the brake lightly and you'll still get regen. I didn't check using the paddle but I assume that it also engages the brake light too.

 

I realize this is an old thread and there are several threads dealing with how the brake lights work when in Low. My question is why didn't GM trigger the brake lights to come on when regen is happening? Seems like a much more secure method as opposed to a measure of deceleration...

 

Just guessing they wanted to simulate how an automatic transmission would slow down. I like that I can switch to 'D' mode after passing someone and let the car slow back down to speed knowing that I get some regen but no brake lights.