TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

AP Braking when highway changes

Discussion in 'Model 3: Driving Dynamics' started by mreynolds767, Dec 27, 2019.

  1. mreynolds767

    mreynolds767 Member

    Joined:
    Jul 11, 2019
    Messages:
    726
    Location:
    Boston
    While not a major issue, I would put this under more of a minor annoyance.
    Curious if an issue for others as well.

    A couple of areas I routinely drive; the highway I am on changes to another highway. There really is no turn off or similar so one does not lower their speed or anything similar in these examples.
    The car if in AP at say 75 will abruptly brake to 55 which can be a problem if a car is close behind ; as there is logical reason to brake here. Has to be something in the map telling the car of a speed limit / road change or something that is causing it.

    Main location is where Rt. 3 heading north ends and becomes Rt. 95 / 128 south of Boston.
    Any way to change the car's behavior in these commonly driven places?
     
  2. Knightshade

    Knightshade Well-Known Member

    Joined:
    Jul 31, 2017
    Messages:
    10,887
    Location:
    NC
    Yeah the speed limit is based on map data. If the speed limit drops the car slows down. Worked as designed.
     
  3. mreynolds767

    mreynolds767 Member

    Joined:
    Jul 11, 2019
    Messages:
    726
    Location:
    Boston
    While it makes sense it can be a dangerous situation.
    As in this case, it is a multiple lane highway with absolutely no reason to brake ; or I should say there may be a legal reason to drive slower but in practice zero cars brake here.

    Rough guess Rt. 3 is a 60 MPH zone and when it becomes 95/128 it is a 55 MPH
    If I had AP on 75 it should not go all the way down to 55 ; if it is going to reduce speed it should be to 70 (5 MPH less to match)
    That would at least not be dangerous.
     
  4. ewoodrick

    ewoodrick Well-Known Member

    Joined:
    Apr 13, 2018
    Messages:
    5,285
    Location:
    Buford, GA
    It definitely sounds as if the speed limit is charging, or you are greatly exceeding the apees limit and the speed resets.
     
  5. mreynolds767

    mreynolds767 Member

    Joined:
    Jul 11, 2019
    Messages:
    726
    Location:
    Boston
    Am positive the speed limit changes here but is a minor change.
    Goes from what is a 60 MPH or 65 MPH highway to a 55 MPH highway ; still the rate of travel/speed of the cars does not lower.
    And if I was previously exceeding the speed limit why does the change cause Telsa to reduce my speed to match the limit?

    This particular area often has traffic at all hours so not always going to be affected but the way the car currently reacts here is not like any human driver would and that is my point.
     
  6. ewoodrick

    ewoodrick Well-Known Member

    Joined:
    Apr 13, 2018
    Messages:
    5,285
    Location:
    Buford, GA
    The speed is going to set to the new speed plus the amount specified in the settings. If you have it set to +7 and you are in a 65 going 75, and then go into a 50, then the car will slow from 75 to 55.
     
  7. mreynolds767

    mreynolds767 Member

    Joined:
    Jul 11, 2019
    Messages:
    726
    Location:
    Boston
    Ah thank you!
    I think I have that setting at 0 currently so if I change that to plus 15 that should be better for me
     
  8. TydalForce

    TydalForce Member

    Joined:
    Nov 24, 2019
    Messages:
    219
    Location:
    West Chester, PA, USA
    It's kind of a murky area; on the one hand, you >technically< shouldn't be going so fast. On the other hand, the car shouldn't suddenly decelerate when it could do so more gradually.
    You might want to do a "Bug Report" next time it happens.
     
  9. mswlogo

    mswlogo Well-Known Member

    Joined:
    Aug 27, 2018
    Messages:
    5,799
    Location:
    MA, NH
    I set my offset to -20 which kills the car from applying speed changes and greatly reduces phantom breaking.
     

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC