Active Cruise Control... Not Quite So Active?

[thefuturenow]

One of my i3's few disappointments thus far has been the Active Cruise Control. At best, it whizzes along with slightly more intelligence than a standard cruise control. At its worst, it's a worrisome piece of technology that feels unreliable. Perhaps the system is just now being demystified as an owner as the documentation and videos online pre-purchase were vague, but it wasn't a major selling point for me anyway. Admittedly, I fully expected the system to adjust speed to match speed limits (it already has the speed limit sign readings, what gives?) and also to brake for traffic but I found myself a few feet away from some driver's bumpers while using it heading up to a braked vehicle when I decided the ACC and collision avoidance systems were being worthless set on early avoidance as well as maximum following distance and intervened.

In very initial testing, it lacks the ability to utilize speed limit information to adjust speed and is too unreliable to trust to properly brake so, really, what good is it?

 

[jadnashuanh]

I don't know of any cruise control that will adjust the set speed based on the speed limit. Might be one, but I doubt it. You set the desired speed, and you can adjust the following distance, and it should never run into the car ahead of you. It errs on the side of safety, and especially if the lane markings aren't clear, can have issues on a curvy road about something being in your lane, and, because it is camera based verses laser or radar, it has issues with deep shadow or low angle sunlight, but I do find it pretty good, and use it extensively. My other car does not have it, and when I do drive that, find the lack of following safely is annoying. When that gets replaced, the new one will also have this feature. FWIW, you'll usually get better range when using it, too...it's much better at keeping your set speed unless the road has lots of hills than you can do, and even there, it's not bad.

 

[stumbledotcom]

…it lacks the ability to utilize speed limit information to adjust speed…

You're disappointed by the absence of a feature you dreamed up in your own head?

Wow.

 

[thefuturenow]

…it lacks the ability to utilize speed limit information to adjust speed…

You're disappointed by the absence of a feature you dreamed up in your own head?

Wow.

The Tesla Model S does it, and while I accepted that it won't stay in its lane in the U.S. like Tesla Autopilot, I just assumed after seeing the speed limits posted next to the speedometer in a test drive that one of the reasons for that was so the ACC can adjust for speed. That would be a simple software update for BMW to release since the technology is there.

 

[epirali]

Admittedly, I fully expected the system to adjust speed to match speed limits (it already has the speed limit sign readings, what gives?) and also to brake for traffic but I found myself a few feet away from some driver's bumpers while using it heading up to a braked vehicle when I decided the ACC and collision avoidance systems were being worthless set on early avoidance as well as maximum following distance and intervened.

I personally think the ACC worked well with two exceptions:

1) The camera is a little too easily confused and gives up. I understand when its blinded by direct sunlight and/or heavy rain or fog. But there are a few occasions where it decided a few too many alternating light/shadow regions is an issue.

2) I wish it wouldn't just drop out and kick in regen, which actually has been fixed in the latest update (may have to get it just for that).

But I have never had it not stop with cars ahead. If anything very rarely it over reacts, but never under reacts and has not been a safety issue. In fact in traffic I use the feature as a "speed limit" by setting it higher than the speed limit and letting the car ahead set my pace.

 

[Jonathan]

I too have wished that it would auto adjust for posted speed limits. However, then I realized that whenever I go through a school zone that has a 15mph sign, it auto reads that regardless of time or day. I have also driven over a highway bridge and read a 70mph sign. So I no longer think it is a good idea.

What does the Tesla do when it goes through a school zone and reads a sign that isn't valid for that time of day?

 

[thefuturenow]

Admittedly, I fully expected the system to adjust speed to match speed limits (it already has the speed limit sign readings, what gives?) and also to brake for traffic but I found myself a few feet away from some driver's bumpers while using it heading up to a braked vehicle when I decided the ACC and collision avoidance systems were being worthless set on early avoidance as well as maximum following distance and intervened.

I personally think the ACC worked well with two exceptions:

1) The camera is a little too easily confused and gives up. I understand when its blinded by direct sunlight and/or heavy rain or fog. But there are a few occasions where it decided a few too many alternating light/shadow regions is an issue.

2) I wish it wouldn't just drop out and kick in regen, which actually has been fixed in the latest update (may have to get it just for that).

But I have never had it not stop with cars ahead. If anything very rarely it over reacts, but never under reacts and has not been a safety issue. In fact in traffic I use the feature as a "speed limit" by setting it higher than the speed limit and letting the car ahead set my pace.

I hypothesize that perhaps the main reason it didn't stop for me was the battery was close to full when I tried it so there wasn't enough capacity to regen or I wouldn't completely rule out driver error although it got dangerously close without me intervening so even if I had accidentally disabled the ACC and turned on dynamic cruise control the collision system should've intervened before I had. Good to know that the latest update fixes the dangerous behavior of the ACC when it disables though.

 

[thefuturenow]

I too have wished that it would auto adjust for posted speed limits. However, then I realized that whenever I go through a school zone that has a 15mph sign, it auto reads that regardless of time or day. I have also driven over a highway bridge and read a 70mph sign. So I no longer think it is a good idea.

What does the Tesla do when it goes through a school zone and reads a sign that isn't valid for that time of day?

Good points you bring up, as the Tesla Autopilot in its current incarnation would just follow the school zone speed limit with no regard for posted times. As the driver still has to be alert the driver would be responsible for manually setting the correct speed outside of school hours.

 

[Boatguy]

I too have wished that it would auto adjust for posted speed limits. However, then I realized that whenever I go through a school zone that has a 15mph sign, it auto reads that regardless of time or day. I have also driven over a highway bridge and read a 70mph sign. So I no longer think it is a good idea.

What does the Tesla do when it goes through a school zone and reads a sign that isn't valid for that time of day?

Good points you bring up, as the Tesla Autopilot in its current incarnation would just follow the school zone speed limit with no regard for posted times. As the driver still has to be alert the driver would be responsible for manually setting the correct speed outside of school hours.

The Tesla will set the speed to the current speed zone (plus a user specified offset), but only in response to a pull on the TACC stalk. It will not increase or decrease the speed when the speed limit changes. So if you go from a 45 to 35, it's going to continue at 45 unless you again pull and hold the stalk to set the TACC.

That nit aside, I've been using the i3 ACC for almost 2yrs and I think the ACC works pretty well. It's not as good as the Telsa for resuming after coming to a full stop in traffic, but I've had no issues with it following/stopping. It is of course sensitive to the following distance set by the driver and if set to the closest setting it will definitely brake later and harder.

And just as with the Tesla, it will at times accelerate when approaching stopped cars which are either out of its camera range, or that it has not yet decided are stopped. It sees the vehicle but doesn't seem to judge or use the distance/speed information until it's quite a bit closer. So the human driver will look down the street, see cars stopped at a light and not accelerate, while the Tesla and i3 will both accelerate, then decelerate/brake.

 

[jadnashuanh]

FWIW, if the battery is full (or nearly so) and there's no room for regen to put that energy, the car WILL use the brakes to slow down and it's pretty close to the same effect as regen, and many people may never notice. IOW, doesn't matter on the SOC, the car reacts the same way.

 

[thefuturenow]

FWIW, if the battery is full (or nearly so) and there's no room for regen to put that energy, the car WILL use the brakes to slow down and it's pretty close to the same effect as regen, and many people may never notice. IOW, doesn't matter on the SOC, the car reacts the same way.

I'm trying to give the i3 some excuse for appearing that it wasn't going to brake at all, but I can't find one. I even checked the make sure the forward collision warning was on.

 

[Boatguy]

FWIW, if the battery is full (or nearly so) and there's no room for regen to put that energy, the car WILL use the brakes to slow down and it's pretty close to the same effect as regen, and many people may never notice. IOW, doesn't matter on the SOC, the car reacts the same way.

I'm trying to give the i3 some excuse for appearing that it wasn't going to brake at all, but I can't find one. I even checked the make sure the forward collision warning was on.

The car doesn't need an excuse, I believe it was going to stop. The problem is that as experienced driver's we sum up the situation and don't want to wait to find out; we quite literally have a longer perspective than the ACC camera and act rather than wait, as we should.

When my i3 or Tesla starts accelerating and I see a car at a red light in front of me, many years of driving experience say "NO" and I take over control.

ACC and Tesla's TACC and Autopilot are all driver assistants, they are not autonomous driving programs; we're still in charge. If we feel the assistant needs to be overridden we should do it. But it doesn't mean the automation is broken or wrong, it just has a different threshold than we do.

 

[jadnashuanh]

I agree...I look at the ACC as a tool, but it is not an autonomous driving tool (yet). If you expect it to be, you will run into problems. I look at it as a smarter 'normal' cruise control. IMHO, it will take more than a camera to provide automated driving. ACC is just a small step above the 'normal' cruise control we've had for decades.

 

[jmatero]

My system was a little flaky lately so took it in and the service manager drove with me for some time and saw the same problems. They reset the system and re-calibrated the camera and it's working pretty flawlessly now. The re-calibration requires them to drive 12 miles the paperwork stated.

 

[thefuturenow]

Is it normal behavior for forward collision to not intervene if I have it set to early and let me end up inches from someone's bumper? Even without ACC enabled, I figured forward collision should work 90% flawlessly.

 

[jadnashuanh]

The forward collision system relies on the ultrasonic sensors, and then only at low speeds. Those sensors do not have a lot of range. You get a bit more distance with the active cruise control's camera. How soon it will start to slow down seems to be a combination of whether you're following someone that is slowing down, approach a car that has brake lights on, or approaching a car without brake lights, but stopped. How smoothly and abruptly the i3 slows seems to get worse and more abrupt as you progress in that set of conditions I listed...smoothly as someone is also slowing that you've been following, decent if the stopped car has brake lights illuminated, and much more abruptly (and later) if they're stopped without brake lights currently on. The camera is looking at image size and angle of view It's already decently calibrated to what you are following, but when approaching something that you were not following from a distance, it takes time to figure out what's what.

 

[Boatguy]

Is it normal behavior for forward collision to not intervene if I have it set to early and let me end up inches from someone's bumper? Even without ACC enabled, I figured forward collision should work 90% flawlessly.

If I'm approaching a car in what it thinks is too quickly, I'll get a warning from the forward collision system; but that's obviously from the camera as it's not close enough for the ultrasonics. Only once or twice has it intervened and slammed on the brakes, both times for pedestrians when it was not actually necessary.

If you think the system isn't working take it in and have the service advisor drive with you and/or ask them to re-calibrate it. It's a safety feature and I wouldn't rely on comments from the forum.