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Cruise control inappropriately slamming on brakes

mckince

New Member
Jun 27, 2020
3
11
UK
Hi, first post here.

I'm having significant issues with the adaptive cruise control. There is a 2 lane road near me with a 50 limit, and I like to set the cruise to stop me speeding. However, on a couple off occasions the cruise control has hammered on the brakes when a truck has been coming the other way - despite being safely and completely in its own lane.

I have had the same thing on motorways; overtake something, then pull back into the middle lane with a lorry in the inside lane. The cruise control seems to think that I am going to drive into the lorry and, again, hammers on the brakes.

It is lucky that I haven't had anyone smash into the back of me. I've had to stop using cruise on 2 lane roads and hover my foot over the accelerator when anywhere near a lorry on the motorway in case it decides to randomly fire me through the windshield.

Am I alone in this?
 

Stach

Member
Mar 23, 2019
489
285
Madison, WI
Welcome to the phantom braking "party", which has been going on for far too long (years). Unfortunately TACC is considered Beta software, even though it's the only cruise control offering that Tesla has, so they don't really seem to listen or care about it, even though it scares the C#)(&# out of me, and others. I opened a service request for 2 phantom braking incidents, with video documentation and a bug report filed, and they just cancelled my service request without ever even reaching out to me...
 
Last edited:

mckince

New Member
Jun 27, 2020
3
11
UK
Thanks all, looks like I'll have to put up with it for a while at least. It's a shame - this and the blooming automatic wipers are distracting from what has been an otherwise fantastic car.

Finally "2 lane road huh. Doesn't that still fall under the warning limitation in the manual?"

No. It says "Traffic-Aware Cruise Control is primarily intended for driving on dry, straight roads, such as highways and freeways. It should not be used on city streets."

So maybe my UK A road doesn't fit with that, but its the emergency stops on the motorways (freeways) that are most likely to cause an accident and concern me most.

Plus - I'd like a modern car to behave at least as well as my old ones.....
 

lbowroom

Plaid, white with black, CF, 19’s. Delivered 8/27
Sep 12, 2018
1,623
3,799
Orange County
Plus - I'd like a modern car to behave at least as well as my old ones.....

you may not appreciate this, but TACC is paying attention to every 360 threat potentially around your car. Your “better” old cars only concerned themselves with following distance to whatever was directly in front of them.
 

KenC

Active Member
Sep 4, 2018
3,950
3,648
Maine
Hi, first post here.

I'm having significant issues with the adaptive cruise control. There is a 2 lane road near me with a 50 limit, and I like to set the cruise to stop me speeding. However, on a couple off occasions the cruise control has hammered on the brakes when a truck has been coming the other way - despite being safely and completely in its own lane.

I have had the same thing on motorways; overtake something, then pull back into the middle lane with a lorry in the inside lane. The cruise control seems to think that I am going to drive into the lorry and, again, hammers on the brakes.

It is lucky that I haven't had anyone smash into the back of me. I've had to stop using cruise on 2 lane roads and hover my foot over the accelerator when anywhere near a lorry on the motorway in case it decides to randomly fire me through the windshield.

Am I alone in this?
Is your 3 tracking in the middle of its lane according to the visualization? What does the visualization show when it slows on a 2-lane with a truck approaching? Just wondering if the calibration is correct. For some reason, your car seems to think the truck is not safely and completely in its own lane.

When you pull back into a middle lane, I've not heard of anyone else complain of a potential collision with the inner lane, causing a slowdown. This also leads me to wonder if there's a camera calibration issue.

I would have someone video from the back seat, this motorway behavior and show it to your Service Center, because I think it's a uniquely odd behavior and not the typical "phantom braking" that others have already mentioned. You can have the cameras recalibrated.
 

strider

Active Member
Oct 20, 2010
3,699
1,134
NE Oklahoma
you may not appreciate this, but TACC is paying attention to every 360 threat potentially around your car. Your “better” old cars only concerned themselves with following distance to whatever was directly in front of them.

I don't appreciate it BECAUSE IT DOESN'T WORK!!!!! TACC should not be using Autopilot logic. It should be using the radar in the front and that is it (which is what it did when I bought the car 2 years ago). I expect phantom braking when on Autpilot, even though it should not slam on the brakes on a bright sunny day on a US interstate in Oklahoma (read: it's freaking straight and wide) simply because I'm approaching an overpass and it sees a shadow on the road. But now I get phantom braking on TACC. I want to go back to regular "stupid" hold a set speed cruise control. Only Tesla could cock up cruise control.

I'm not angry at your comment. What you said was absolutely correct. I just don't want it to do that :p

@mckince welcome to TMC!

Who specifically said the code rewrite is to address phantom braking? Source?
I think the code rewrite is to address the 6,000 ways in which Autopilot tries to kill me any time I switch it on. Phantom braking is one of those ways.
 

GtiMart

Active Member
Nov 13, 2019
1,808
1,675
Quebec City, Canada
Yes, many of us are now asking for a dumber cruise control that mostly just follows distance with the radar, because of these phantom braking issues. Mind you, I would prefer that the issues would just be fixed but it'S a very difficult problem to solve. In the meantime, I would take a TACC that doesn't provide as much safety features (** because of the false positives **).
 

Knightshade

Well-Known Member
Jul 31, 2017
14,005
24,413
NC
I don't appreciate it BECAUSE IT DOESN'T WORK!!!!! TACC should not be using Autopilot logic. It should be using the radar in the front and that is it (which is what it did when I bought the car 2 years ago). I expect phantom braking when on Autpilot, even though it should not slam on the brakes on a bright sunny day on a US interstate in Oklahoma (read: it's freaking straight and wide) simply because I'm approaching an overpass and it sees a shadow on the road. But now I get phantom braking on TACC. I want to go back to regular "stupid" hold a set speed cruise control. Only Tesla could cock up cruise control.

I'm not angry at your comment. What you said was absolutely correct. I just don't want it to do that :p

@mckince welcome to TMC!


I think the code rewrite is to address the 6,000 ways in which Autopilot tries to kill me any time I switch it on. Phantom braking is one of those ways.



This is not a tesla or autopilot problem.

It's an inherent problem in all existing radar-based braking systems.

Numerous other auto makers have it even worse- including safety recalls in some cases and class action lawsuits.

Couple of examples-

Phantom Braking Leads to Mazda 3 Recall - The Truth About Cars.

Mazda recalling tens of thousands of cars for phantom braking issues.


U.S. probes 553,000 Nissan Rogue SUVs for unintended emergency braking

NHTSA investigating over half a million nissans for unintended emergency braking


I DO expect the re-write to significantly improve things though.
 

TLLMRRJ

Active Member
Dec 19, 2019
2,073
2,488
Houston
I appreciate the links. The few times I have had TACC in rental cars I have not had an issue.

I do wish Tesla would just let you switch off TACC for regular hold a speed cruise control. For those of us that live in places without traffic, it is all you need.

True. It's a sign of incredible arrogance, denial and disregard for the customers that causes Tesla not to offer basic speed-hold cruise control. It would be extremely easy for them to add a software option to the settings menu to switch to good old basic cruise control.

But then again, look at the mess with auto wipers, and auto headlights, etc etc etc
 

Kevy Baby

Dis-Member
Supporting Member
Aug 11, 2019
2,247
2,370
Brea, CA
AP used to be, IMO, nearly flawless. Phantom braking was almost non-existent for me - maybe once per month if that.

Then, earlier this year, things started going down hill. It was right around the time of the last maps update (March I believe), though I am not 100% certain it was because of that. Now, phantom braking has gotten much worse and there are several places that I consistently get max speed reductions (from whatever I am set on to 55 MPH). The exact location of these occurrences moved by a couple of hundred yards on a recent update, which was really weird. I've gotten so used to them, I have my thumb ready on the wheel to flick it back up when they occur.

And phantom braking is much worse as well. Oddly, I have one that occurs in the same place, but only in one specific LANE of a two-lane HOV lane (for those familiar with the area, the left lane of the HOV lane on the 5 South right when passing under Main St. in Santa Ana, right after the Orange Crush - never happens in the right HOW lane).

I am trying to remain optimistic that this upcoming rewrite improves on things.
 
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Kevy Baby

Dis-Member
Supporting Member
Aug 11, 2019
2,247
2,370
Brea, CA
I've experienced phantom braking, and the slowdown is relatively dramatic.

But I wouldn't describe it as "slamming on the brakes." Are other people's experiences more radical than mine? No locked wheels, right?
It's a subjective observation. When it comes as a surprise, the perception is that it is much more aggressive than if one is expecting it. But for me, it is some fairly aggressive braking: so much so that I have semi-seriously considered getting a light-up sign to put in the rear window: "Sorry: it's not me, it's the f-ing car."
 

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