[gramboda]

Weird question...Does anyone know if the brake lights illuminate when adaptive cruise is slowing you down in traffic or maintaining distance?

[Qsilver7]

By design, if the brakes are applied to slow the car down, the rear brake lights should illuminate. If the car is only using engine compression to slow the car down, then no...the brake lights do not illuminate.

Sum:

• brake application to slow or lower forward trajectory...illuminates the brake lights
• engine compression used to slow or lower forward trajectory...does NOT illuminate the brake lights

[gramboda]

Qsilver7
Thanks! Is it safe to assume the vehicle is not applying its own brakes in traffic? Rather, it is using engine compression to slow the vehicle down/maintain distance? Thus, no brake lights.

[avi66]

Originally Posted by gramboda

Qsilver7
Thanks! Is it safe to assume the vehicle is not applying its own brakes in traffic? Rather, it is using engine compression to slow the vehicle down/maintain distance? Thus, no brake lights.

Depends on the traffic conditions. Afaik it applies the brakes more often than not to maintain the set distance.

[astrohip]

Originally Posted by Qsilver7

By design, if the brakes are applied to slow the car down, the rear brake lights should illuminate. If the car is only using engine compression to slow the car down, then no...the brake lights do not illuminate.

Sum:

• brake application to slow or lower forward trajectory...illuminates the brake lights
• engine compression used to slow or lower forward trajectory...does NOT illuminate the brake lights

That's a very informative non-answer.

The question remains, "Do the brake lights illuminate when adaptive cruise slows you down?".

avi66 comes closer with an answer, but even they aren't sure.

Any experts?

[Qsilver7]

Originally Posted by astrohip

That's a very informative non-answer.

The question remains, "Do the brake lights illuminate when adaptive cruise slows you down?".

avi66 comes closer with an answer, but even they aren't sure.

Any experts?

Here's another "non-answer" then....if adaptive cruise is utilizing the brakes to slow the vehicle down...then YES...the brake lights will illuminate. If adaptive cruise is NOT using the brakes but just letting up on the throttle to slow the vehicle down...then NO...the brake lights are not going to illuminate.

Adaptive cruise control does both...it may let up on the throttle...or it may apply the brakes. Depending on which method it uses to slow the car down...relates to if the brake lights come on or not.

If an "expert" does an experiment and reports back...I'm pretty sure that's what the outcome will be. Throttle/engine compression to slow the vehicle down results in no brake lights. If the brakes are applied to slow the vehicle down...the brake lights will illuminate.

Experts...please chime in with your results.

[gramboda]

astrohip

Exactly! Thought it was just me. I guess I need to get around to testing in traffic with someone behind me. HA!

The reason I am asking is because I have about a 25 mile commute on a busy interstate. I rely on the adaptive cruise quite often and I DON'T want to be that guy applying his brakes incessantly when slowing down or maintaining distance. If I knew for sure the brake lights were coming on, I would be less inclined to use cruise on heavier traffic days.

(Disclaimer for future posters: I don't need a lecture about using adaptive cruise on busy highways. Thanks)

[Sportstick]

Originally Posted by gramboda

astrohip

Exactly! Thought it was just me. I guess I need to get around to testing in traffic with someone behind me. HA!

The reason I am asking is because I have about a 25 mile commute on a busy interstate. I rely on the adaptive cruise quite often and I DON'T want to be that guy applying his brakes incessantly when slowing down or maintaining distance. If I knew for sure the brake lights were coming on, I would be less inclined to use cruise on heavier traffic days.

(Disclaimer for future posters: I don't need a lecture about using adaptive cruise on busy highways. Thanks)

You've identified the key characteristic that completely turned me off to ACC...too many close calls with unneeded brakes to achieve the following distance of someone cutting in when a human would just ease off the throttle. But, if the brakes really are going on, I'd want the brake lights. As is, when I did try ACC, had too many guys behind me almost in my trunk. I was describing this to an engineer at another European OEM and he laughed, saying that ACC works well for how Europeans drive, but not so much for Americans and how they regard proper lane-changing behavior.

[CFonAir]

The simple answer is, the lights come on if the car applies the breaks. On rainy days, I've been able to see my brake lights in the window of the car behind me. From a light perspective, it behaves exactly like it would if you were manually driving.

[avi66]

Originally Posted by Sportstick

You've identified the key characteristic that completely turned me off to ACC...too many close calls with unneeded brakes to achieve the following distance of someone cutting in when a human would just ease off the throttle. But, if the brakes really are going on, I'd want the brake lights. As is, when I did try ACC, had too many guys behind me almost in my trunk. I was describing this to an engineer at another European OEM and he laughed, saying that ACC works well for how Europeans drive, but not so much for Americans and how they regard proper lane-changing behavior.

We have our share of dicks that cut in, but I’ve never had any issues with DAP in these situations. It’s never slammed the brakes on despite drivers cutting in.

Also how hard/aggressive it accelerates etc is influenced by driver experience mode.

I use every time I’m on the motorway, so thousands of miles usage.

What do you do when driving manually if a car cut you up very close ?

[avi66]

Originally Posted by gramboda

astrohip

Exactly! Thought it was just me. I guess I need to get around to testing in traffic with someone behind me. HA!

The reason I am asking is because I have about a 25 mile commute on a busy interstate. I rely on the adaptive cruise quite often and I DON'T want to be that guy applying his brakes incessantly when slowing down or maintaining distance. If I knew for sure the brake lights were coming on, I would be less inclined to use cruise on heavier traffic days.

(Disclaimer for future posters: I don't need a lecture about using adaptive cruise on busy highways. Thanks)

Seriously, you’re worried about the brake lights coming on ?

[Shaun170]

Yes they do. I saw mine reflecting on the car behind the other day in low light levels.

[bbb83]

Originally Posted by gramboda

astrohip

Exactly! Thought it was just me. I guess I need to get around to testing in traffic with someone behind me. HA!

The reason I am asking is because I have about a 25 mile commute on a busy interstate. I rely on the adaptive cruise quite often and I DON'T want to be that guy applying his brakes incessantly when slowing down or maintaining distance. If I knew for sure the brake lights were coming on, I would be less inclined to use cruise on heavier traffic days.

(Disclaimer for future posters: I don't need a lecture about using adaptive cruise on busy highways. Thanks)

I'd be more concerned the computer eating the brakes doing these small adjustments all the time. Brake jobs are expensive on these cars if you don't know how to do the work yourself

[Bob in IL]

Originally Posted by gramboda

astrohip

Exactly! Thought it was just me. I guess I need to get around to testing in traffic with someone behind me. HA!

The reason I am asking is because I have about a 25 mile commute on a busy interstate. I rely on the adaptive cruise quite often and I DON'T want to be that guy applying his brakes incessantly when slowing down or maintaining distance. If I knew for sure the brake lights were coming on, I would be less inclined to use cruise on heavier traffic days.

(Disclaimer for future posters: I don't need a lecture about using adaptive cruise on busy highways. Thanks)

I've thought about this too because I don't want to be that guy either. I have to look closer, but with the widespread availability of adaptive cruise, it doesn't seem like I've seen a big increase of brake lights flashing on and off on the expressways or toll roads.

[astrohip]

Originally Posted by Qsilver7

Adaptive cruise control does both...it may let up on the throttle...or it may apply the brakes. Depending on which method it uses to slow the car down...relates to if the brake lights come on or not.

Thank you for more information. Your first response didn't say what you said above. Now that I know ACC does both, it makes more sense.

[Qsilver7]

[JSY]

It is as Qsilver7 says as I've experienced this many times at night on unlit highways. It's it's using the brakes to slow you down, the lights come on. If it's just letting off on the throttle, then no lights. I've wondered the same in the past only to witness it myself.

[Sportstick]

Originally Posted by JSY

It is as Qsilver7 says as I've experienced this many times at night on unlit highways. It's it's using the brakes to slow you down, the lights come on. If it's just letting off on the throttle, then no lights. I've wondered the same in the past only to witness it myself.

That logic makes perfect sense as it mimics human behavior. The remaining issue (at least for me) is how often and how hard the system decides to brake if or when merely easing the throttle would be sufficient.

[JSY]

Originally Posted by Sportstick

That logic makes perfect sense as it mimics human behavior. The remaining issue (at least for me) is how often and how hard the system decides to brake if or when merely easing the throttle would be sufficient.

From what I can tell, it's trying to maintain the size of the gap between you and the car in front of you, so if the car in front of you is slowing down gradually, it will just ease off. However, if they slow down quicker, and the gap is going to get smaller than what you set at a faster rate, ACC would react more urgently and use the brakes to try to maintain that gap. So, I totally think from my experience is that it depends on what it needs to do to maintain the gap in front of you.

[Sportstick]

Originally Posted by JSY

From what I can tell, it's trying to maintain the size of the gap between you and the car in front of you, so if the car in front of you is slowing down gradually, it will just ease off. However, if they slow down quicker, and the gap is going to get smaller than what you set at a faster rate, ACC would react more urgently and use the brakes to try to maintain that gap. So, I totally think from my experience is that it depends on what it needs to do to maintain the gap in front of you.

I completely understand. My point is that ACC can overreact and excessively decide to use the brakes or the degree of suddenness of braking when a human might realize the goal can be accomplished with throttle release. This is exacerbated by Americans’ habit of cutting into a lane with tight spacing.

[JSY]

Originally Posted by Sportstick

I completely understand. My point is that ACC can overreact and excessively decide to use the brakes or the degree of suddenness of braking when a human might realize the goal can be accomplished with throttle release. This is exacerbated by Americans’ habit of cutting into a lane with tight spacing.

Oh, no doubt. It has happened and if it's to an extent that it might create a dangerous situation, I would simply intervene manually. It's truly a system that requires human attention. I'm guessing that's how other cars' systems are as well. That said, I really like it. However, I'm not one that uses it as if it was auto-pilot of some sort.

[DL335D]

Originally Posted by Sportstick

You've identified the key characteristic that completely turned me off to ACC...too many close calls with unneeded brakes to achieve the following distance of someone cutting in when a human would just ease off the throttle. But, if the brakes really are going on, I'd want the brake lights. As is, when I did try ACC, had too many guys behind me almost in my trunk. I was describing this to an engineer at another European OEM and he laughed, saying that ACC works well for how Europeans drive, but not so much for Americans and how they regard proper lane-changing behavior.

The brake lights 100% go on. Can you image if they didn’t? ACC is absolutely amazing and I use it the entire 20 mile drive to and from my sons school. I will never buy a car without it. In stop and go traffic it makes commuting so much more enjoyable. The system pretty much brakes just as I would. It’s pretty freaking amazing.