ACC Motorway sudden unexpected hard breaking

Faults and Technical chat for the Volkswagen ID.3
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MaN
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Joined: Mon Sep 06, 2021 3:52 pm
Location: North Yorkshire

Post by MaN »

We had just collected our new car and the salesman, James, knew we were going on a journey from North Yorkshire to Luton Airport. The car was driven with the ACC on and for the most part worked well. Certainly made the journey more relaxed and enjoyable. On the way back from Luton Airport after the very 1st junction after Leicester, with an over motorway roundabout the ACC applied the breaks very hard unexpectedly which worried me alot especially when thinking about the traffic travelling behind. The very next junction with an over motorway roundabout the ACC did the same. I turned the ACC off after that. Has anybody else experienced this

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smuj
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Post by smuj »

There are a number of threads here about this. The ACC uses the Satnav data and the camera to read the speed limit road signs. Seems that the ACC picks up false speed limits and acts on them, either speeding up or braking, often heavily like in your case.

In one of the earlier threads on this someone posted how to switch this function off. This is one of the first things I will do once I receive my car. Perfectly happy with the way the ACC works on my Tiguan.
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Jamh2000
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Post by Jamh2000 »

Yes it does this - but it’s only very occasional (e.g. sometimes when there is a small road with a different speed limit nearby). Not an issue for me. Also I think the system won’t brake so as to slam you into the cars behind - it is designed to slow you safely and is generally aware of what is around you.
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monkeyhanger
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Post by monkeyhanger »

OP: So you were driving under an overpass roundabout on the motorway? I suspect your issue is that the Sat Nav doesn't think 3 dimensionally, so it assumes you took the roundabout route, rather than the straight road underneath. I only really use ACC through average speed camera zones, and everything the car intends to do something I don't want it to, it only takes a tiny dab of accelerator to cancel it out. It should be doing a bit of regen braking before it jumps on the brakes last second.
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ENEMUK
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Post by ENEMUK »

Aside from the danger, I think the present level of driver assistance systems requires more effort on the part of the driver than is worth it. Using ACC, in traffic or coming up to slow traffic, my foot is hovering on the brake. What if the car doesn't slow to a stop? It also takes an age to get going again. Only a few seconds, but much longer than a human driver.

The time spent anticipating the driver assistance systems is more effort for me than driving the car - which is itself a pleasure. I do use it, partly for fun/experimentation and it is v. good for keeping to the speed limits in areas where they change a lot or in average speed zones (as monkeyhanger said above).

The most amusing (irritating?) message I get is please 'take the steering wheel' or words to that effect. This is when I wander over or even towards the central line.
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Post by G43FAN »

ENEMUK wrote: Tue Sep 07, 2021 6:35 am Aside from the danger, I think the present level of driver assistance systems requires more effort on the part of the driver than is worth it. Using ACC, in traffic or coming up to slow traffic, my foot is hovering on the brake. What if the car doesn't slow to a stop? It also takes an age to get going again. Only a few seconds, but much longer than a human driver.

The time spent anticipating the driver assistance systems is more effort for me than driving the car - which is itself a pleasure. I do use it, partly for fun/experimentation and it is v. good for keeping to the speed limits in areas where they change a lot or in average speed zones (as monkeyhanger said above).

The most amusing (irritating?) message I get is please 'take the steering wheel' or words to that effect. This is when I wander over or even towards the central line.
The late braking in traffic is slightly un-nerving but my Tiguan's ACC was the same Will it, Won't it adventure.
With regards to getting going, I bet more Human drivers run into the back of the car in front that moved then stopped than ID.3s will. That point something of a second could be justified prudence.
Asking you to take the Steering Wheel when you wander is the car doing what it's supposed to do. Stay in lane and it doesn't do it? (or indicate a lot) Would you rather it came up with a message that said, " See, what happened there is you wandered across the line and hit the front of that truck. I could see it happening but thought I'd wait to see if you were really driving or not. Seems you weren't, shall I call an Ambulance?"
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Utumno
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Post by Utumno »

ENEMUK wrote: Tue Sep 07, 2021 6:35 am Aside from the danger, I think the present level of driver assistance systems requires more effort on the part of the driver than is worth it.

As a counterpoint to this view, driver assistance systems, and specifically adaptive cruise control, permit Mrs U to be safer while driving, more alert, less tired, and avoid (or at least delay) having to make specific vehicle adaptations to support her disability. Similar arguments can be made for matrix headlights and lane keeping assist.
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ENEMUK
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Post by ENEMUK »

I get that there are advantages :D and of course for some use cases or drivers there are important benefits.

The lag when starting off after coming to an automatic stop is sometimes so long that I assume the ACC has switched itself off (or that I have somehow inadvertently overridden it). Understood that this is safer and better than bashing into the car in front. :)
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