[Kraven]

Recently I was driving southbound in San Diego and had two new experiences while using the ACC in moderate to heavy traffic on the freeway. The time of day was approx. 3:30PM in the afternoon, with daylight beginning to wane a little. I'll say upfront, windshield was perfectly clean across the entire glass including where the camera is) I had been using ACC (which I know uses the radar in the grill, maybe some assist from the camera as well) for many miles and the traffic at this point was stop and go, getting up to maybe 15MPH and sometimes to a complete stop. On this one occasion, the vehicle in front of me came to a gradual and complete stop and the Volt was not stopping, traveling slowly. The front collision warning came on (it really shouldn't do that in this situation as ACC was on and had been for quite some time) and at that point I applied the brake and stopped the Volt.

The second incident happened about 15 minutes later, again keep in mind sun is low in the sky. I went under a bridge that work was being done on, there were wooden tressels that broke up the sunlight as I was going under it. This time the front collision warning flashed again on the windshield and the beeps happened, but there was NO car in front of me at all. The brakes were applied by the front auto braking for a fraction of a second, then the brake was released and I kept on my way.

I believe both of these incidents were related to light conditions due to time of day, as well as the rapid breaks in that light caused by the wooden tressels. I thought about the Tesla fatality with the truck due to lighting conditions, lack of contrast between the sky and the tractor trailer.

I know ACC and Forward Automatic Braking, nor any system in a car, is perfect. This is why we need to be vigilant and use these aids wisely. I won't use ACC if I have a tailgater behind me. I won't rely on ACC if I see traffic stopped ahead and the person behind me is back by even a "normal" distance, I'll brake myself gradually as ACC will stop more abruptly/later than I would.

I thought I'd share this experience as I haven't seen it before. Definitely (obviously) need to stay alert when using the ACC, still overall awesome tech/feature including the front collision alert and auto braking. Will certainly improve when all cars "talk" with each other and take some of these other factors out of the equation.

 

[Loboc]

In very slow stop and go traffic, no matter the lighting conditions, ACC can stop detecting the lead car (the car icon turns off). Happens all the time on my commute. No icon, no automatic braking.

 

[hellsop]

I thought I'd share this experience as I haven't seen it before. Definitely (obviously) need to stay alert when using the ACC, still overall awesome tech/feature including the front collision alert and auto braking. Will certainly improve when all cars "talk" with each other and take some of these other factors out of the equation.

Presuming there's never a "not-talking" antique in the road. And actual collision avoidance will STILL need cameras and radar, because even the talking part won't have the precision necessary to state with absolute assurance whether the car that said it's 50 meters in front of yours is in the same lane as you, or whether it's not, in fact, only 40 meters in front instead. GPS just isn't THAT precise between two independent receivers. (If you can slave them together so that they're one system with local connections between, then sure, you can get the differential between them down to a centimeter or two. But two random cars on the same road? That's not one system, that's two, and each one is only going to be RELIABLY +/- about 10 m. Which means the two cars above that yours thinks is 50m away from the position it reported could be as close as 30m or as far as 70m, and without radar or cameras to say differently, it's gambling with a collision as stakes.)

 

[Whatstreet]

Presuming there's never a "not-talking" antique in the road. And actual collision avoidance will STILL need cameras and radar, because even the talking part won't have the precision necessary to state with absolute assurance whether the car that said it's 50 meters in front of yours is in the same lane as you, or whether it's not, in fact, only 40 meters in front instead. GPS just isn't THAT precise between two independent receivers. (If you can slave them together so that they're one system with local connections between, then sure, you can get the differential between them down to a centimeter or two. But two random cars on the same road? That's not one system, that's two, and each one is only going to be RELIABLY +/- about 10 m. Which means the two cars above that yours thinks is 50m away from the position it reported could be as close as 30m or as far as 70m, and without radar or cameras to say differently, it's gambling with a collision as stakes.)

I am not disagreeing with you regarding the need for vision and or lidar systems. But using GPS should be secondary. We need location tags in the road.

 

[bakedpatato]

Yeah, I've had that happen to me before, kinda scary especially when there's no car...the system's emergency braking is very powerful too (thank you Bosch!)

If I see cars coming to a complete stop in front of me I temporarily disable the system and brake manually especially as I brake smoother than the system in said situation...thankfully the system can resume at any speed once it sees a car

 

[Kraven]

In very slow stop and go traffic, no matter the lighting conditions, ACC can stop detecting the lead car (the car icon turns off). Happens all the time on my commute. No icon, no automatic braking.

I understand when the icon is off, no automatic braking as it doesn't see a car ahead. The question is, what factors lead to the icon turning off? I think overall ACC works great, it just isn't 100% and isn't advertised by GM as "autopilot" or perfect or anything like that. Keep in mind Volts with ACC are quite new, and I wonder just how long it will be until we hear about a driver getting too confident with this tech and having a problem. It does not at all replace the driver requirement to be 100% attentive, it is however good enough to possibly cause some drivers from giving 100% attention at all times.

 

[bakedpatato]

I understand when the icon is off, no automatic braking as it doesn't see a car ahead. The question is, what factors lead to the icon turning off?

The icon turns off when the FCA camera and the radar can't see a car in front of you; I can see that happening if the sun shines right into the camera and traffic is slow enough for the radar to not be able to filter out noise vs the car in front of it

 

[klchiew]

One other thing to note is that the long range radar sometimes get confused with the fairing on 18 wheel tractor trailers, the ones that has an extension below the center of the trailer for aero reasons. I've had 2 instances where the auto brake engaged (not obtrusively, but enough for you to feel the brakes engage), but the system re-calibrates quickly back to normal.

It's hardwired to me now whenever I use ACC, especially in heavier traffic conditions that I hover my left middle finger on the re-gen paddle on the steering wheel. I feel that pulling the paddle quickly disengages ACC faster than hunting for the cancel/off button or moving your feet towards the brake pedals. The re-gen paddle has dual use!

 

[Arcanox]

The re-gen paddle has dual use!

Actually, fun tidbit, it has another use: I've found when in charge-sustain mode, when nearly coasting, the engine isn't as quick to shut off as other hybrids I've driven. Usually tapping the regen paddle will make it think you're about to brake, and shut the engine off. Then you can resume coasting in EV mode until the battery drops too far. You don't even need to tap it long enough to actually start braking...just enough to confuse the computer! It's like a Swiss Army Paddle!