I am loving my new car, nearly a week old now. The ACC is great but does a few flaky things sometimes. I was passing a slip road with no one in front of me. A car had gone up the slip road and there was a car behind me. I was doing a constant 73mph when my car decided to brake quite unexpected to just under 70mph. Whats all that about? Do you think it is just moisture on the front sensor? It did a similar thing on the way home from work the other night, again I had just passed a slip road off.

Mine has done it three or four times recently. A bit disconcerting!

Mine used to do it but I went into set up and changed the distances from the factory default and its fine now. Nearly had a 40 tonner in my boot on day one when the car braked unexpectedly (and unnecessarily).

 

Just now, skidpan said:

Mine used to do it but I went into set up and changed the distances from the factory default and its fine now. Nearly had a 40 tonner in my boot on day one when the car braked unexpectedly (and unnecessarily).

Hi. I have the distance as 2 bars. Is that the setting you mean? 

The ACC thinks you're going to crash in to the back of the car that's slowing down on the slip road, it has no way of knowing that they've left the main road and can only assume the road goes that way and you're going to follow them.  If there's another car ahead going straight on, it can detect that the road splits and will ignore the car on the slip road.  The work around is to anticipate the situation and press the throttle to override the ACC braking.

I think you need a deep understanding of ACC to avoid or work around situations like this, and the information provided in the Skoda handbook is woefully inadequate.

2 minutes ago, D402 said:

The ACC thinks you're going to crash in to the back of the car that's slowing down on the slip road, it has no way of knowing that they've left the main road and can only assume the road goes that way and you're going to follow them.  If there's another car ahead going straight on, it can detect that the road splits and will ignore the car on the slip road.  The work around is to anticipate the situation and press the throttle to override the ACC braking.

I think you need a deep understanding of ACC to avoid or work around situations like this, and the information provided in the Skoda handbook is woefully inadequate.

Thanks but the car in the slip road is miles to the left side and it's got a  concrete barrier and low wall in between so not sure how it's picking that up. I am to the right of it anyway so it should know I was overtaking if it can see it anyway.

It does seem to be particularly bad in these situations.  Radar gives very accurate range but coarse direction.  It's probably still picking up the car on the slip road and just on the edge of being able to predict a collision within the margins of error of its estimates.  It won't know you're passing to his right or about the barriers (which won't reflect back to the sensor strongly enough); up to a point, it'll assume the road goes where he's going and you're going to follow.

37 minutes ago, D402 said:

It does seem to be particularly bad in these situations.  Radar gives very accurate range but coarse direction.  It's probably still picking up the car on the slip road and just on the edge of being able to predict a collision within the margins of error of its estimates.  It won't know you're passing to his right or about the barriers (which won't reflect back to the sensor strongly enough); up to a point, it'll assume the road goes where he's going and you're going to follow.

Maybe will just have to press on accelerator slightly then if I see people leave at a junction just in case. Seems a bit silly having to do that though.

You said " The work around is to anticipate the situation and press the throttle to override the ACC braking"

Surely if it thinks you are going to crash into that car than accelerating will make it brake even more????

 

Had a couple of these "jolts" but generally its a great system.  Maybe it's built in just to check you're awake.

No, your actions have priority just like in normal cruise control.  A dab of throttle will prevent it from trying to slow you down and leave ACC active for when you're past the slip road, you braking would cancel ACC braking but also cancel ACC, and slow you down of course.  Unfortunately, it's a fundamental problem when the only sensor is radar.

I guess your L&K has the camera for lane guidance; I thought that it might provide lane and vehicle information to improve the ACC capability but your experience suggests not.

Just now, D402 said:

No, your actions have priority just like in normal cruise control.  A dab of throttle will prevent it from trying to slow you down and leave ACC active for when you're past the slip road, you braking would cancel ACC braking but also cancel ACC, and slow you down of course.  Unfortunately, it's a fundamental problem when the only sensor is radar.

I guess your L&K has the camera for lane guidance; I thought that it might provide lane and vehicle information to improve the ACC capability but your experience suggests not.

I haven't tried lane assist yet, i turned it off. Maybe I should give it a go.

3 minutes ago, tigermad said:

I haven't tried lane assist yet, i turned it off. Maybe I should give it a go.

 

Just be careful on roads with no/worn painted lines

I use ACC a lot and have not come across this at all. The only issue I have had was in slower moving traffic (about 30mph) on a motorway when the car was keeping a gap to the car in front, just as this was accelerating and i was starting to also a car pulled into the gap and the ACC simply didn't detect it. I left it for a few seconds to see what it was doing. I am sure if I hadn't braked it would have slowly driven into the car. Just reminded me that it can't be relied on 100%.

2 minutes ago, Mickey43 said:

 

Just be careful on roads with no/worn painted lines

Why what does it do? I assume nothing, or will it try and make you go in the middle of the road as if its 1 big lane?

Edited 7 April, 20179 yr by tigermad

53 minutes ago, tigermad said:

Why what does it do? I assume nothing, or will it try and make you go in the middle of the road as if its 1 big lane?

 

If the lines are worn or not there at all (eg nearside concrete walls only) then the system won't "see" anything so won't correct if you stray over.

 

Works brilliantly when lines are there though.

Edited 7 April, 20179 yr by Mickey43