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Autopilot brake-checking HGVs in slow traffic

Twice now I've had an unpleasant situation in slow traffic where Autopilot starts brake-checking HGVs that are close behind. There's nothing shown on the display to suggest that there's a reason for panic-braking, and it happens continually even with traffic in front a long way away.

Basically it'll stamp on the brake, and if you intervene with the accelerator and lift off again it'll do exactly the same thing. If you don't do anything it'll slow to about 5mph, then accelerate again to about 25 before repeating the hard stop.

The only consistent element is that both times an HGV has been following close behind. I don't know if this is confusing the cameras but it's worth keeping a very close eye on. Happens in both .28 and .36.
 

yessuz

Active Member
Dec 30, 2021
1,729
1,235
Midlands
Twice now I've had an unpleasant situation in slow traffic where Autopilot starts brake-checking HGVs that are close behind. There's nothing shown on the display to suggest that there's a reason for panic-braking, and it happens continually even with traffic in front a long way away.

Basically it'll stamp on the brake, and if you intervene with the accelerator and lift off again it'll do exactly the same thing. If you don't do anything it'll slow to about 5mph, then accelerate again to about 25 before repeating the hard stop.

The only consistent element is that both times an HGV has been following close behind. I don't know if this is confusing the cameras but it's worth keeping a very close eye on. Happens in both .28 and .36.
do you have cars infornt?

because that's how stupid vision rather than radars behaves, like "Is there a car? no. go go go.. oh sheet, there is car. brake! nope, no car - go go go"
 
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Mrklaw

Active Member
Mar 5, 2020
1,912
1,259
Berkshire
do you have cars infornt?

because that's how stupid vision rather than radars behaves, like "Is there a car? no. go go go.. oh sheet, there is car. brake! nope, no car - go go go"

hate this so much. In queuing traffic AP should be a god-send but its so violent I turn it off both for my comfort and avoiding frustrating people behind me.

Just use the ‘creep’ speed as the gap grows and then blend in from there. How hard can it be?
 

Ben_

Member
Jan 4, 2022
39
22
.
The risk of phantom braking on motorways or A-roads in traffic scares me, frankly. I wish I could trust the car implicitly, but I cannot. I can only assume that the driver of the car behind me assumes I’m just driving like an idiot, when the car decides it randomly needs to drop the anchors. Even a 5mph or 10mph lift makes a big difference to traffic when you’re on a busy motorway.
 
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Every car I have driven recently with any "smart" cruise control has had phantom braking occur in congestion.. It is going to happen until the technology matures, if you don't like it, don't an early adopter. My Tesla has done it once to me already (just picked it up on Monday), it was a pleasant experience when you compare it to my 2018 Optima. It slams on the brake and locks up the emergency brake. When this happens I have to turn off the car and turn it back on to release the emergency brake. Imagine this happing when going 50 mph in SoCal traffic!
 

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