Radar ACC and automatic braking?

[s7wag]

So I was driving up the motorway yesterday with my ACC set and was heading for a build-up of slower traffic which led me to move to the second lane and as I did so the brake lights came 'on' in the car in front of me for what seemed like no reason which led me to take caution and brake too and now I'm thinking WTF as the next car head seemed to be quite a distance ahead...

Now this led me to start thinking about what the ACC does on my Golf when the car ahead is drifting to within the set distance set on the computer and whether this is normal for it to 'brake' to slow down and maintain the distance, which would replicate what I'd just suffered...what appeared to be a random braking of the car in front when it didn't really appear necessary?

Anyone have an idea on how the car behaves with ACC on in terms of braking to slow-down or letting off the gas or both to maintain the 'safe' set distance?

Anyone else experienced what seems like a senseless random braking on the car in front?

 

[vidman]

There could be many reasons for apparently random brake lights,

It could be he does have his ACC set with a long gap setting, many people do not know it is adjustable

It could be an early warning that there is slow traffic ahead and he will be slowing down

He might just be getting ready to brake and touched the brake peddle causing the light to come on

He could just be a poor or nervous driver

or anyone of many other reasons

 

[richiekuk]

I would like to know the same, as there's nothing worse than someone braking all the time for no reason.
I'd hate to think my ACC is making it look like I'm one of these "brakers"!

 

[pcr]

I find it's a bad habit to make any assumptions about what the car in front might do, he could have made an emergency stop.

 

[richiekuk]

I find it's a bad habit to make any assumptions about what the car in front might do, he could have made an emergency stop.

I totally Agree, if not a little off subject.

 

[s7wag]

yeah, I get all the safety aspects BUT my wondering was in the light of what would have been a large safety gap set on ACC (it was a VW Passat) it just got me thinking that if my ACC did the same a lot of people would be thinking what a tw*t!!

So, "Anyone have an idea on how the car behaves with ACC on in terms of braking to slow-down or letting off the gas or both to maintain the 'safe' set distance?"

 

[s7wag]

I find it's a bad habit to make any assumptions about what the car in front might do, he could have made an emergency stop.

No assumptions made...I had no concern about the driver ahead doing an emergency stop or different as I was in control of my car and aware of my surroundings...I made the statement that traffic was slowing down ahead, a lorry in front of me in inside lane, hence I was moving to 'middle' lane with a car just passing me before I did so, a large gap between that car and traffic ahead. As I move across, he was still a distance ahead of me BUT his brake lights came on...HENCE my question in relation to ACC and the car's behaviour in relation to the ACC - Does the car brake to maintain the set distance, does it just back-off the throttle (as you would do manually to start with) , or what does it do?

 

[aew003]

Does the car brake to maintain the set distance, does it just back-off the throttle (as you would do manually to start with) , or what does it do?

I can feel my car breaking in order to maintain the pre-set distance. Recently, on a motorway, a lorry pulled out (without indication or warning) on me causing the car to automatically apply quite a significant amount to braking force to prevent me rear ending it.

 

[vidman]

I do not think there is any way of controlling the ACC behavior other than setting the distance to maintain via the strearingwheel controls - there are 3 distances, long, medium and close - but how the ACC controls the speed up/down within those distances is down to the ECU programming

 

[s7wag]

Interesting! @aew003 yes, I've felt the same in those situations and I think I can deduce that we are also all guilty of the passive breaking from the ACC system maintaining the set distance too then!

Thanks all