1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Adaptive Cruise - Presense question

Discussion in 'New A3/S3 (8V Chassis)' started by Itguy, Mar 14, 2014.

  1. Itguy

    Itguy Well-Known Member

    Joined:
    Oct 25, 2013
    Messages:
    1,130
    Likes Received:
    449
    Hi everyone

    Does anyone know what can trigger pre-sense warnings with ACC?

    I thought it was all due to distance but going to work the other day it triggered when a very slow moving car pulled into my lane quite far in the distance (75m ish). I was travelling at about 50mph and they were probably doing 20mph but accelerating.

    This triggered my pre-sense warning but it didn't brake for me as I was just about to override the ACC brake anyway.
     
  2. Advert Guest Advertisement


  3. Cockney Boy

    Cockney Boy Member

    Joined:
    Nov 26, 2007
    Messages:
    481
    Likes Received:
    6
    What car have you got?
     
  4. Itguy

    Itguy Well-Known Member

    Joined:
    Oct 25, 2013
    Messages:
    1,130
    Likes Received:
    449
    As per sig - new S3
     
  5. snowfree52

    snowfree52 Full LED baby !

    Joined:
    May 27, 2013
    Messages:
    531
    Likes Received:
    125
    It's the difference in velocity that triggers the presense.
     
  6. Itguy

    Itguy Well-Known Member

    Joined:
    Oct 25, 2013
    Messages:
    1,130
    Likes Received:
    449
    Yes, that certainly seems to be what happened to me. I don't know why but I always thought it was distance related?
     
  7. snowfree52

    snowfree52 Full LED baby !

    Joined:
    May 27, 2013
    Messages:
    531
    Likes Received:
    125
    well it's related. presense sees you are still accelerating that means you didn't see the car, and it starts to brake when it thinks it's the last chance before the accident
     
  8. RossR

    RossR Active Member

    Joined:
    Apr 27, 2013
    Messages:
    501
    Likes Received:
    121
    Like the adaptive cruise it's looking at three things - distance, difference in speed and difference in rate of acceleration (or deceleration).
     
  9. cemerson

    cemerson Well-Known Member

    Joined:
    May 9, 2013
    Messages:
    4,210
    Likes Received:
    922
    If it suddenly sees a car that it didn't see before, I think it's cautious for a bit until it can work out that it isn't a threat. If the car wasn't accelerating then it was probably just about to slow down. I've not seen the pre-sense warning come up in mine though for similar situations.
     

Share This Page