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Old 07-11-2011, 02:07 PM
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ACC and Brake Lights

I use the ACC all the time, love it, and can't imagine using just plain old cruise control. I'm so comfortable with it that I will actually let it slow from a cruising speed of 75mph down to 20-30mph (right before I get the !BRAKE! alert on the evic.

My question pertains to the brake lights when ACC is engaged. Does anyone know how the brake lights function when the vehicle is slowing? I feel like I might be pissing off the guy behind me because my brake lights are constantly turning on/off when the sensor is adjusting to the vehicle in front of me.

Had my buddy follow me to observe and he told me that the brake lights never turned on even when slowing significantly.

I was under the impression that ACC uses a combo of throttle control and braking to maintain distance from vehicle in front of you. I would surely hope that the brake lights aren't always on/off at minimal speed adjustments but should definitely be coming on when the vehicle is slowing signficantly.

Sorry if this has been posted/discuss elsewhere.
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Old 07-12-2011, 01:37 PM
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Re: ACC and Brake Lights

As I understand it, the brake light only comes on when the brake is applied...just like driving...but not when less accelerator or downshifting...just like driving.
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Old 07-12-2011, 01:51 PM
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Re: ACC and Brake Lights

this is one of the OMG posts.

sorry to be hating on technology but I would suspect that using the ACC to decelerate the vehicle from highway to 10-20 MPH in regular driving is NOT what the makers intended. while its a 'way cool' feature considering their is no warning to the driver behind you I would be cautious in its use.

I am so alarmed by this post and use of the ACC in such a way that i will file a complaint with the NHTSA. I consider this THAT MUCH of an issue for those of us that may be behind you/

rant over/
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Old 07-12-2011, 02:02 PM
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Re: ACC and Brake Lights

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Originally Posted by robpp View Post
sorry to be hating on technology but I would suspect that using the ACC to decelerate the vehicle from highway to 10-20 MPH in regular driving is NOT what the makers intended. while its a 'way cool' feature considering their is no warning to the driver behind you I would be cautious in its use.
Honestly, I don't see an issue with that. If you are going 75mph in a 20 year old car without ACC and simply take your foot of the gas, I'd assume the circumstances wouldn't be any different. If brakes are applied, the brake-lights are on. Again, no difference. In addition to that, you seem to forget that ACC adjusts to the current traffic-pattern. If the car using ACC decelerates from 75 to 20, the car in front decelerates in the same way - once again, no difference. Just as you would do without ACC in order to avoid a collision.

If a car is getting slower without braking, the driver behind has NO CASE at all. The first thing you learn while driving is to obtain a secure distance behind the car in front of you.
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Old 07-12-2011, 02:07 PM
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Re: ACC and Brake Lights

if it didnt matter we would NOT have brake lights/

IMO the brake lights are there to let the guy behind KNOW you are slowing down or stoping......while I agree i could use my parking brake and trans in ANY vehicle to stop it or slow it without TRIGGERING the brake lights IMO its not the safest way to do it/ both for you the driver and for the person behind you.

while we argue it out in court hopefully no one got hurt in the accident/

this can actuallly be done in any car with cruise just using the buttons....its the same thing. so while I COULD use my cruise control to slow or stop my vehicle without letting the driver behind me KNOW, i CHOOSE to use my brake pedal so there is no mistake,,,,,i am braking/
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Old 07-12-2011, 02:08 PM
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Re: ACC and Brake Lights

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Originally Posted by robpp View Post
this is one of the OMG posts.

sorry to be hating on technology but I would suspect that using the ACC to decelerate the vehicle from highway to 10-20 MPH in regular driving is NOT what the makers intended. while its a 'way cool' feature considering their is no warning to the driver behind you I would be cautious in its use.

I am so alarmed by this post and use of the ACC in such a way that i will file a complaint with the NHTSA. I consider this THAT MUCH of an issue for those of us that may be behind you/

rant over/
Let me rephrase since some of you may be taking this out of context. What I am trying to say is that in conditions where traffic gradually slows I am very comfortable with the ACC adjusting accordingly. Remember, I said before the !BRAKE! warning comes on the evic, not when it comes on. Did the "makers" not intend for it to work this way? If not, then why wouldn't the system alert !BRAKE! much sooner? Maybe I was too heavy in my op, more like 30-40mph.

My original question was that, if someone is tailgating you and your vehicle slows before you tap the brake yourself does the driver behind you know you are slowing? In some cases, even in a gradual slow down the driver behind you may not realize you are slowing when ACC is engaged if brake lights do not come on. Trying to avoid a rear collision scenario.

Simple question.
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Old 07-12-2011, 02:14 PM
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Re: ACC and Brake Lights

right and you got the simple answer: No/

so I might ask the next simple question.....does that answer change how you might use the acc in real driving situations?
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Old 07-12-2011, 02:17 PM
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Re: ACC and Brake Lights

Without having looked into it at all or having spent any time in school with it yet, I would imagine its very similar to the anti sway control on trucks that apply individual brakes to stop trailer sway... it uses a calculation for how quickly the vehicle is decelerating to deturmine if the brake lights are needed. If there is a situation where you slow quickly enough I am sure the lights will come on.

I remember one of my instructors talking about the 300c he was driving one time with the adaptive cc set when a car got onto the freeway and cut him off and as the vehicle pulled infront of him the 300 mashed on the brakes throwing him into his seatbelt. I am sure in this instance the brake lamps came on
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Old 07-12-2011, 02:26 PM
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Re: ACC and Brake Lights

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Originally Posted by 2005JGC View Post
Without having looked into it at all or having spent any time in school with it yet, I would imagine its very similar to the anti sway control on trucks that apply individual brakes to stop trailer sway... it uses a calculation for how quickly the vehicle is decelerating to deturmine if the brake lights are needed. If there is a situation where you slow quickly enough I am sure the lights will come on.

I remember one of my instructors talking about the 300c he was driving one time with the adaptive cc set when a car got onto the freeway and cut him off and as the vehicle pulled infront of him the 300 mashed on the brakes throwing him into his seatbelt. I am sure in this instance the brake lamps came on

its cruise control....no brake lights/ when the computer is in control; there are no brake lights/ no matter acc, abs, trtaction control, etc.....they all use the caliperr and the brake system to apply braking/stopping yet NONE of them use the brake lights........as far as I can tell/
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Old 07-12-2011, 02:46 PM
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Re: ACC and Brake Lights

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Originally Posted by robpp View Post
its cruise control....no brake lights/ when the computer is in control; there are no brake lights/ no matter acc, abs, trtaction control, etc.....they all use the caliperr and the brake system to apply braking/stopping yet NONE of them use the brake lights........as far as I can tell/
What I am talking about is reaction time. Think of it this way - when you are following someone at highway speeds and you see their brake lights come on you usually tap your brakes, sometimes even at a safe distance behind the guy in front of you, right? Now let's say you have ACC engaged and you are constantly fluctuating speeds 5-15mph (between 60-75mph). Ultimately everyone will encounter a driver behind them, whether they are following close or at a safer distance. How does that driver know you are slowing when ACC is engaged? I just assumed that ACC taps brakes (brake lights illuminate) as a typcial safety manuever upon speed fluctuation. Maybe there is a threshold. Are we saying that the system doesn't do this?
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Old 07-12-2011, 02:53 PM
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Re: ACC and Brake Lights

actually i have been doing some research and the system, if it uses the brakes, should be illuminating the brake lights, according to the NHTSA.

not when its coasting or free wheeling per se, only if it applies the brakes then it should flash the lights on.

that was the main part of my angst.......no brake lights but it seems as if it does this., or should/ some early versions, other makers, lincoln is one, did NOT light the lights and then had to change that once it became apparent.

and yes I guess reaction time feeds into it......
if the puter hits the brakes hard the person following may not have proper time to ever stop unless the lights come on....
if its just not accelerating and coasting thenm the follower would have all sorts of reaction time/ like an older manual cc
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Old 07-12-2011, 02:56 PM
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Re: ACC and Brake Lights

Quote:

Reading FAIL
This is via dealerconnect on adaptive cruise control operation.... Again I am fairly certain there there is a deceleration threshold that when the vehicle is commanded to slow outside of that threshold that legally a vehicle must notify drivers behind. Very different but similar to the anti sway control I mentioned.
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