[AudiA4]

Originally Posted by Dan203

I got the auto specifically for this feature. It's pretty neat but not sure if it's really required or not.

Before having ACC (again, on the Volvo), I assumed it was mainly a convenience feature. While that is true, its best attribute is that it's a safety feature.

[GoranBonn]

Long time lurker here, finally registered to add some of my observations to ACC. When selecting my car (2013 330d, my first BMW) this was one of the must-have gadgets I wanted, and have tried it in various conditions over the past year and a half of owning my car:

1. ACC WILL NOT BRAKE if you are approaching an ALREADY STOPPED vehicle at a traffic light. This can be particularly dangerous if you are following a moving vehicle slowly coasting towards a traffic light, and the vehicle in front of you decides to switch to a different lane, leaving you with a bit more road in front and an already stopped vehicle ahead.

My guess is that the reason for this is technical: the system is presumably ignoring all radar reflections coming back as stationary objects (i.e. detected by radar as coming at it at current driving speed), as otherwise it would react to shrubbery along the road, signposts, potholes etc. I'm guessing that's basically the side effect of this data being filtered out on purpose. The stuff that doesn't get filtered is anything moving at a different speed from yours - the system will catch bikers and cyclists without a problem.

2. If you were wondering how it feels to be driven by ACC: it behaves like a driver with tunnel vision seeing only one car in front of them. Most important difference between ACC and a human driver is that the human driver will look beyond the first car ahead and will adapt the distance to the immediate car in front also based on expectation of the front car's reactions to traffic ahead. Without this, and only trying to react to the front car, does not provide for a completely smooth stop&go traffic.

In my experience, driving in stop&go traffic, I found that ACC will often brake when I personally would not have. I would have instead either slowed down to increase distance to the car ahead of me or coasted closer to it, in order to smooth out the necessary braking for the cars behind me. Occasionally I'd like a sign on the back of my car saying "sorry that's ACC braking" I could switch on

3. Someone was mentioning abrupt braking. Interestingly, one of the BMW technical manuals said that the ACC system accelerations are using the learning / adapting of the throttle response to individual driving style. What this means is the car learns what is your usual acceleration you are presumably comfortable with, and when accelerating with ACC, will use that acceleration. Can't remember if same was true about brakes, but might be. Also the acceleration with ACC is different depending whether you are in Eco Pro or Comfort mode.

4. I've noticed ACC is very intelligent in how it handles lane changes and coming to a different speed vehicle in the other lane. It is fully capable of not immediately jumping on brakes, but instead will coast and lightly reduce speed until they match, even sacrificing car distance for a brief moment if the speeds are close enough. Also if you shift to an empty lane and your speed is relatively close to your preset ACC speed, it will very very smoothly get up to the targeted speed. On the other hand, if your set speed is much higher, it will accelerate properly just as you would.

5. The one thing that impresses me the most is how good the radar is in following cars on curved highways. I'm still not sure how they do it, but imagine the following: you are on a 3-lane highway in the center lane. In front of you is a car to which your ACC is locked on to with 3 bars distance, so quite some way away (4-5 car lengths). To his right is a truck in the right lane, going more slowly. The highway gets to a left curve. The car and truck in front already reach that curve. Now if you were to draw a straight line from the radar on your car directly forwards, the radar is "looking at" the truck, yet it seems to me the system somehow compensates for this.

I'm not sure if it's the KAFAS camera doing some magic with detecting road turns (I don't have lane departure warning, but do have speed limit info), or the effect is a combination of reading the position of the steering wheel and pointing the radar slightly left/right, coupled with some data filtering from signals far enough to be considered unreliable.

6. Driving in rain or fog won't stop the system. Actually it was a great help when driving through some serious fog, as it made following the car in front much easier and made me feel like having an additional safety net to following visually his taillights in the fog.

7. In snow, the slush will collect on the radar sensor and the system will give up and tell you that ACC is no longer available. HOWEVER, there's no fallback to "normal" cruise control. At that point you don't have cruise control, period. My guess this is intentional, as otherwise you may forget you are cruising in "blind" mode. But would have been nice to have graceful degradation of the system.

8. Getting people to experience ACC for the first time is a lot of fun! Some of them get seriously freaked out at not braking and leaving the car to come to a stop on its own. For me as well there was a learning curve to get myself not to intervene with braking (as well as realizing the limits of the system in point 1 above). There were some butt-clenching moments of unexpected braking by the car in front of me on the highway that produced the collision-warning angry beep-beep but also a safe slowdown from 130 kmh to 60 kmh with no problems whatsoever (except the wife's comments ).

In any case the thing works seriously impressively! Just like the surround view. And the engine. And the gearbox. And the adaptive headlights. And sport mode. And the torque. And ... everything.

[Livetodrive]

I like the ACC too. I did notice that if the speed is set too high, once the traffic clears the car tends to over accelerate after restarting from a stop. The trick is to lower the speed set point to a reasonable value, say 25 or 30 mph, when stuck in traffic. I only use it on the highway.

[RM7]

Originally Posted by Dan203

I got the auto specifically for this feature. It's pretty neat but not sure if it's really required or not.

Last weekend I spent 3hrs going about 50 miles in really slow moving traffic due to a wildfire. It's a godsend.

[eluded]

Get a Tesla, it has autopilot. Way better than this adaptive cruise control[IMG]https://s.aolcdn.com/hss/storage/mid...adrive1_v2.gif[/IMG]

[Dan203]

Originally Posted by eluded

Get a Tesla, it has autopilot. Way better than this adaptive cruise control[IMG]https://s.aolcdn.com/hss/storage/mid...adrive1_v2.gif[/IMG]

A bottom of the line Tesla Model S costs more then a maxed out 340i. So it's not like these two cars are in the same class and just interchangeable between buyers. (decently equipped Model S costs about $100k)

[Kabrich]

Originally Posted by SteveinArizona

I said I had two Priuses and the active cruise control was a more basic version...no stop and go but it do slow up and speed up based on the radar view of the car in front of it.

And again, Prius has not had that feature for "almost 10 years".

[Kabrich]

Originally Posted by eluded

Get a Tesla, it has autopilot. Way better than this adaptive cruise control[IMG]https://s.aolcdn.com/hss/storage/mid...adrive1_v2.gif[/IMG]

Unless a white truck pulls out in front of you.

[kadify]

Originally Posted by GoranBonn

7. In snow, the slush will collect on the radar sensor and the system will give up and tell you that ACC is no longer available. HOWEVER, there's no fallback to "normal" cruise control. At that point you don't have cruise control, period. My guess this is intentional, as otherwise you may forget you are cruising in "blind" mode. But would have been nice to have graceful degradation of the system.

So you never have the option to use just a regular cruise control? I find that interesting since both of my parents cars that have ACC have a way of just cruising without the radar part on.

[GoranBonn]

Originally Posted by kadify

So you never have the option to use just a regular cruise control? I find that interesting since both of my parents cars that have ACC have a way of just cruising without the radar part on.

Correct. If you have snow on your ACC radar the warning message that ACC is unavailable and the radar should be cleaned comes up and goes away, but the check control warning triangle remains on the dash. If you try activating cruise control again, it will say it's not available.

I'm guessing the behaviour you describe is on some other manufacturer's cars?

[RM7]

Originally Posted by kadify

So you never have the option to use just a regular cruise control? I find that interesting since both of my parents cars that have ACC have a way of just cruising without the radar part on.

You have the option, there's a button, just not if it packs with slush as you are driving. For the record, I drove all winter in Alaska and this happened once, on the highway when it was snowing heavily above freezing temp.

[Dan203]

There is? Where? It seems to me that ACC is always on when I enable cruise control on my new 340i.

[kadify]

Originally Posted by GoranBonn

Correct. If you have snow on your ACC radar the warning message that ACC is unavailable and the radar should be cleaned comes up and goes away, but the check control warning triangle remains on the dash. If you try activating cruise control again, it will say it's not available.

I'm guessing the behaviour you describe is on some other manufacturer's cars?

Yes different manufacturer but I would assume that they wouldn't take away an entire feature if conditions are unsuitable for the radar... I would assume there is some sort of work around.

[RM7]

Originally Posted by Dan203

There is? Where? It seems to me that ACC is always on when I enable cruise control on my new 340i.

below the left vent

[Dog Face Pony Soldier]

I am addicted to cruise control in general; Active Cruise Control makes this tool worlds better.

Before I owned my car (with ACC of course) I imagined how spectacular this tool would be in stop-and-go traffic. Now that I have a bit over 50k miles I think a little differently.

An example of ACC working spectacularly would be my commute up/down the NJ Turnpike. Set the cruise to 75 mph and toggle the distance to 1-or-2 bars and go. When traffic slows you at 60-65 it's not an issue... Your able to keep the cruise on where "dumb" cruise control would have to be aborted. When traffic opens up you automatically ramp up to your max set speed. Love it.

While I do use ACC in stop-and-go traffic approximately 25% of the time, I usually handle these situations manually. Why? A competent human is simply going to do a better job reading the traffic and adjusting. A tip I would suggest is if you back off the distance bars the system will work more smoothly in stop-and-go traffic.

One other note is the driver can override the system by applying throttle. If you want to control your distance manually you don't need to abort ACC... Just apply throttle. The side benefit is you get braking as soon as you lift off the throttle. This provides ultra-quick brake application.... WITH the braking system primed up! Really nice when people start jousting out there!

Complaints about the system are only in relation to how well a human can handle the same situation. ACC is undoubtedly better than conventional cruise control systems. At this point; no ACC on an M2/3/4 makes those cars undesirable. C-mon BMW! Porsche puts ACC on their cars, you can offer them on an M!

[Dan203]

Originally Posted by JamesNoBrakes

below the left vent

Cool. Never even noticed that button. Looks like there is space there for other buttons. I assume there are probably ways to turn off the other nannies, like lane departure, when equipped with those options? Had I known they could be disabled I might have got the other package. I didn't because I thought the lane departure and blind spot warning stuff might be annoying.

[Dan203]

Originally Posted by glennQNYC

Before I owned my car (with ACC of course) I imagined how spectacular this tool would be in stop-and-go traffic.

I don't live in an area with a lot of traffic. Unless there is road construction or an accident we never have stop and go traffic. At rush hour you might get some slowing near major interchanges, but it never comes to a complete stop.

[Ali Shiralian]

I have it on both the F30 and the Subaru and find Subaru Eye Sight to be a souperior system. For one it doesn't get covered with dirt and snow in winter as it uses cameras and nor radar....

[Dog Face Pony Soldier]

Originally Posted by Dan203

I don't live in an area with a lot of traffic. Unless there is road construction or an accident we never have stop and go traffic. At rush hour you might get some slowing near major interchanges, but it never comes to a complete stop.

ACC works great in those conditions.

[SteveinArizona]

Originally Posted by Kabrich

And again, Prius has not had that feature for "almost 10 years".

Yes...I misspoke. I had the Prius version of active cruise control on my 2011 Prius but not on my 2007.

I have had my car stop at a light (or stop sign) when there are cards in front of me. But that has been when I have been testing the ACC to see how it works. When it did so, all I had to do after the light changed was gently tap the accelerator.