SwedeSpeed - Volvo Performance Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter · #1 ·
What happens if collision avoidance kicks in, like many have experienced even when there is no impending collision, when you are on snow or ice.....is it possible for it to send the vehicle into a slide? From the reports I have seen it is somewhat aggressive when it kicks in.
 

·
Super Moderator
Joined
·
39,263 Posts
What happens if collision avoidance kicks in, like many have experienced even when there is no impending collision, when you are on snow or ice.....is it possible for it to send the vehicle into a slide? From the reports I have seen it is somewhat aggressive when it kicks in.
It should not, as long as you are not going to head into the other car's rear end. If you are turning away from the other car or switching lane, the system will give the brakes a temp "tug" and nothing more. Plus, DSTC will prevent the car from a protracted slide.
 

·
Registered
Joined
·
159 Posts
It's only "aggressive" in so far as it jolts you into heightened sense of awareness - flashing HUD icon, loud sound, preloaded breaks with slight tug and pretensed seatbelts. It's annoying when it's a false alarm (which we assume it always is as we think we are the best drivers ever and we are fully aware of everything) but under assumption that it does it when the car is close to emergency situation it's definitely pitched just right. It doesn't slam the breaks the wheels keep rolling so it should not be sending you into a skid. It does help to have experienced it a few times.

Think about this way - if you nodded off, would you rather be woken by this or by an airbag?
 

·
Registered
Joined
·
826 Posts
So when does collision avoidance hit the brakes? If it thinks a snow drift your going to go through is a car wouldn't hit the brakes then?
 

·
Registered
Joined
·
159 Posts
i've only experienced what I described above. I think it's car telling you that unless you change steering input you should start breaking now - that's what causes the false alarms for me - I do not slow down enough for its liking when I have a car parked halfway into my lane and have not repositioned yet and do not have my foot on a brake. I also get false alarm when I go at constant decent speed around a long sweeping bend with cars parked on the outside so my steering is fixed for that bend curvature but the bend tightens so the car estimates that I will hit the cars on outside if I carry on at this speed as it does not know I am going to turn the wheel a bit more. Whether there is a second stage where it will break for you if say even the steering input change is not enough - I am not sure, perhaps people who have been in collisions or near enough have experienced it - I've seen no mention in the manual when I read about how's the system works. I had the similar system in my Prius and it worked in the same way, xc90 has more false alarms but I imagine it takes more things into account and there are sensitivity settings if needed.

I find when the warning is triggered my foot goes straight onto the break ad it's really quite a warning. Perhaps people had the same thing but then actually pressed the break without realising, thinking it was the car.

Drift/skid has nothing to do with collision avoidance - it would be handled by stability control programme and haldex does apply breaks to individual wheels for shifting torque to get best traction but not for slowing down the car. I would imagine it would treat any significant break input from collision avoidance system in the same way as human input - give it a go, if slips - ABS, traction control.

The OP is asking whether crash avoidance slams the breaks (understandable concern as it is not the best strategy in the snow) and the answer is definitely not in regular collision warnings I have been exposed to.
 

·
Registered
Joined
·
559 Posts
The OP is asking whether crash avoidance slams the breaks (understandable concern as it is not the best strategy in the snow) and the answer is definitely not in regular collision warnings I have been exposed to.
But in the videos online of the collision avoidance system being put to work, the system actually does brake the car, since the driver fails to do so. Now, given that there have been cases posted on this forum of the collision avoidance being falsely triggered by drifting snow or splashing water (I think bolinp posted something about this IIRC), there's a very real concern that the system could slam the brakes on say a patch of black ice or something triggered not by a car or a real hazard in front of the car, but merely a snow drift or splash of water from the car in front. And if the brakes were slammed by the car on icy conditions, it could indeed trigger a skid or cause an accident.

I think that is OP's concern. (Very good question BTW)
 
1 - 6 of 6 Posts
Top