adaptive cruise control dropping out

[Pahaska]

I picked up my new-to-me 2019 I3 last Monday. During the drive back from San Antonio in light rain, the cruise control dropped out once and the I3 abruptly slowed. Fortunately, I was not rear-ended.

I live just off a ranch-to-market road with 1 1/2 miles of curves through the Texas hill country. Whether there is a car ahead of me or not, I can not drive that stretch in either direction without the cruise dropping out.

It also dropped out once on a straight stretch of 5-lane, but the sun was directly in the camera and I can understand that.

Do others have this problem? A major reason I upgraded to the 2019 was the adaptive CC. I never had these problems with my previous cars (Genesis).

 

[eNate]

This is my biggest annoyance with the adaptive cruise, which I use regularly. I understand and accept that the camera based system can get confused, but I hate the fact that when it disengages, the car responds by essentially "stepping on the brakes" on the freeway. There should be an override built in that to the system that disables regen and allows the car to coast. That would be much more acceptable.

I've learned to manage it, and cover the accelerator pedal when there are turns on the freeway or potentially system-confusing merges, tunnels, etc. But it's really ill-conceived that the result of ACC flipping off is an aggressive deceleration.

 

[eNate]

Your post got me curious and I did some searching, found a blog post by Tom Moloughney complaining about the same thing 6 years ago. Surely BMW is aware of this and has deemed it not a safety issue. Perplexing.

http://bmwi3.blogspot.com/2014/10/bmw-i3-overactive-active-cruise-control.html

 

[websterize]

Do others have this problem? A major reason I upgraded to the 2019 was the adaptive CC. I never had these problems with my previous cars (Genesis).

I've noticed unexpected ACC dropouts on hilly roads. In these conditions, I tend to cover the go pedal or pause the ACC.

 

[alohart]

Most ACC's use both one or more cameras plus radar. The i3 uses a single low-resolution grayscale camera that is easily confused by sunlight on the its lens, heavy precipitation, a dark underpass under a bright bridge, etc. It's basically early 2010's technology that hasn't been updated.

Old-timers will remember how strong regen kicked in immediately after ACC kicked out in early i3's. That was potentially dangerous. A system software update added about a 1 second delay to the start of regen after the power pedal is released or ACC drops out, and the regen power seems to ramp up a bit rather than starting at full power. This delay allows one to press the power pedal in time to prevent regen if one is prepared to do so (e.g., right foot near power pedal). This has become a non-issue for me after driving our 2014 BEV for 6 years.

 

[eNate]

My 2013 Flex uses radar only (as I believe does my wife's 2016 S60) and the radar gets fooled, too. Usually by metal barriers on bridges that are close to the edge of the traffic lane.

Combining camera and radar seems ideal. I was really suspicious of the i3 when I learned it was camera only, especially since the technology was old (figuring the camera and more importantly the computer doing all the deciphering was initially 2013 vintage equipment).

Strange thing is, the S60 also has a camera, which it uses for reading speed limit signs (just like the i3) and I believe pedestrian detection, and maybe even slow-speed collision avoidance. But from what I can tell, it has nothing to do with ACC (unlike the 2019 Volvo lineup which use both radar and camera for ACC).

I'd like to be driving behind me when the i3 ACC disengages, just to see how fast everything unfolds. When it catches me by surprise, I always feel like I'm a second late to the party, but maybe it looks different to the driver who is removed from the startling BONG of the disconnect.

 

[Pahaska]

I discovered today that a sudden dip in the road reliably cancels the CC.

I went for lunch in the opposite direction from my usual travels. In both directions, at about 55 mph, the same dip in the roadway canceled the CC. In one case, the road ahead was clear, in the other case, I was following a truck.

The dip isn't really that abrupt. It is comfortable to cross it at 55 mph.

Since it happened twice, I turned around and tried both directions again. Sure enough, the CC canceled in both directions. Apparently, the logic can't handle the sudden vertical transition. Maybe it thinks I'm about to run into the pavement.

 

[skeptic]

Let's face it, the ACC in the i3 kinda sucks. Not only does it drop out under many conditions, I think what's worse is when it doesn't slow down for cars stopped ahead of you. I've had a few times where I had to take over and mash the brakes pretty hard when I realized the i3 wasn't going to stop on it's own in time. If I'm nit picky, it's also annoying how long it takes to realize the car turning ahead of you is no longer in the way. Going through town it will nearly stop after a car ahead of you has turned on a cross street. If I'm really really nit-picky, it doesn't have any lane centering or lane keep assist like it should. The hardware is there, EU versions get this at low speeds with the traffic jam assist stuff, no reason other than liability and sub par software to not have some level of auto steering.

However, it's still nice to have and much better than "normal" cruise control. Yes, you have to pay attention, but that's true not matter what kind of cruise control you have or don't use at all. Once you get used to the limitations it's still a great feature. It was one of my requirements for my i3, and if I had to do it over I'd still make ACC a requirement for buying an i3. It's also nice that BMW doesn't charge you $thousands to enable the on button for it.

 

[3pete]

I think what's worse is when it doesn't slow down for cars stopped ahead of you.

I found it very interesting that this is apparently a big challenge for most technology that supports self-driving. Radar ignores most things it sees as stopped because it doesn't have the precision to tell if they're in your lane of travel or outside of it. LIDAR probably is best positioned for stopped vehicles/objects it but has its own flaws, and obviously isn't on the i3.

It's really highlighted in the firetruck example because a giant red truck with flashing lights is probably one of the most visible things for a human but apparently not for "superior" technology.
https://www.wired.com/story/tesla-autopilot-why-crash-radar/

it's also annoying how long it takes to realize the car turning ahead of you is no longer in the way

This is the one I've found to be the most erroneous. I've even had a couple "collision warning" lights pop up because of it when the car was easily going to clear the lane at their speed and I was prepared to brake if they stopped. I can't say I blame it though, I'd rather it err on the side of caution than the alternative!

 

[jadnashuanh]

FWIW, many CC systems say do not use them on hilly, curvy roads, or on slippery surfaces.

100-years ago, southern New Hampshire was mostly farms. Very few today. It used to be a few patches of trees and fields but today, it's about 98% trees outside of a town. The i3 doesn't like the deep shade, sunny spots when there are trees along the road. It's okay if it's totally in shade, or totally in sun (unless the angle is into the camera), but isn't great under some circumstances.

It should be fairly easy to tell if the i3 is going to stop for an obstruction as there either will or won't be a symbol of a vehicle on the driver's display. If you notice you're coming up to a stopped vehicle, and you weren't following it (as indicated in the display), it's best to just manually disengage the CC and coast to your stop, or resume, if that is the best choice. As was mentioned, the original implementation of the software had significantly higher peak regeneration, and, there was no delay. The ACC is not self-driving. You have to be paying attention.

 

[alohart]

I think what's worse is when it doesn't slow down for cars stopped ahead of you. I've had a few times where I had to take over and mash the brakes pretty hard when I realized the i3 wasn't going to stop on it's own in time.

ACC is on whenever I drive which is mostly in suburban or urban driving. I have never had it fail to slow down for stopped cars ahead. However, its low-resolution grayscale camera can't see far ahead enough to begin braking when I would when cars are stopped ahead and I am traveling at 45 mph. By the time it recognizes stopped cars ahead, it friction-brakes to decelerate. In these situations, I disable ACC and allow regen to begin early enough to avoid friction braking.

On several occasions, ACC has failed to recognize a vehicle ahead traveling more slowly than I am. These have typically been white box trucks. I have had to disable ACC to allow regen to decrease my speed.

If I'm nit picky, it's also annoying how long it takes to realize the car turning ahead of you is no longer in the way. Going through town it will nearly stop after a car ahead of you has turned on a cross street.

.
Even when a slower car ahead changes lanes, ACC is always slow to accelerate. In these cases, I just push the power pedal a bit until I reach the ACC set speed.

After 6 years, I'm very accustomed to ACC's weaknesses and am ready to take over temporarily when necessary. The i3 is the only car I've driven with ACC. I miss ACC when I drive a car without it.

 

[jadnashuanh]

When I ordered my first BMW, I didn't opt for the ACC, but it was on the i3 that I wanted, so why not? I have found it to be very useful, and ordered it on my latest vehicle, too. I think the reason why BMW chose to simply rely on the camera was power. A radar would likely end up using more power, so it was a cost/benefit/weight decision. It works, you just need to (eventually) understand it to get the most out of it. You still have to drive the vehicle and take over when prudent. It works much more smoothly if you're following a vehicle than if you come up upon one that is stopped and it hasn't decided there was anything there. That process seems to take awhile to discern. First, it has to recognize there's something there, then determine the closing distance. With a radar, it can see further ahead, and make that decision more accurately and faster. On a relatively low-resolution camera, it's looking for changes in the pixels covered by the image, that it first has to decide if it's an obstacle or not.

While you can spoof a radar, it's easier to obliterate the image in a camera, and then, it shuts itself off. If it bothers you, can always default it to a 'dumb' cruise control, but I don't think that there's a way to do that automatically...you'd have to do it each time you started the vehicle up. How you have your following distance set can affect things, too. If you have it set to short, it will get closer to the vehicle ahead than if you set it to a longer space. Long can give it a bit more time to slow down. I find that setting it to the longest value makes for the smoothest progress. Yes, that might invite people to cut in front of you, but it also gives you a bit more time to stop in an emergency, if that's required, or, to see some debris or pothole in the road that they ran over just before you got there and you'd like to avoid. In the long run, you don't really take longer to get to your destination, and it's more relaxing. I hate it when someone is on my bumper all of the time!

 

[Pahaska]

After driving in 2 heavy rainstorms, the adaptive cruise has started to work fairly well.

I suspect that when the dealer prepared the car, it was washed and waxed. A previous poster had problems with RainX, I think the same thing happened to me with whatever ended up in front of the camera when I bought the car. Rain seems to have been the remedy.

This morning, I drove in light fog in the dark and at noon in the light fog without any problems with the cruise. The only dropout recently was while cresting an overpass into the late afternoon sun.