[2002]

I don’t know if this has been pointed out because I haven’t read the entire thread (I don’t have the patience to read interminably long posts). But the answer is in the owner’s manual.

Thanks for posting that section of the manual about ACC. I notice that it uses the word "braking", which I am thinking is referring to the friction brakes. Myself and others have observed that ACC does not activate the brake lights when it does light regen, but if it gets into heavier slowing then ACC activates the brake lights. If my interpretation of the owners manual is correct that would be consistent with my theory that for heavier slowing ACC adds in some friction brakes.

 

[ClarityDave]

Thanks for posting that section of the manual about ACC. I notice that it uses the word "braking", which I am thinking is referring to the friction brakes. Myself and others have observed that ACC does not activate the brake lights when it does light regen, but if it gets into heavier slowing then ACC activates the brake lights. If my interpretation of the owners manual is correct that would be consistent with my theory that for heavier slowing ACC adds in some friction brakes.

Personally, I think it turns the brake lights on whenever deceleration exceeds a certain amount whether it’s friction brakes or regen. And I believe you would be correct in assuming that ACC will use friction brakes if needed.

 

[2002]

Personally, I think it turns the brake lights on whenever deceleration exceeds a certain amount whether it’s friction brakes or regen.

It does work as you said, due to regulation. Details of the regulation are in post #7.