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Rear ended another vehicle, not blaming Tesla but wondering why AEB did not activate?

kaelandavis1

Member
Jul 24, 2019
10
24
Denver
Hi all,
I recently rear ended someone and when it happened my EAB made no attempt at stopping the vehicle. Long story short- I was merging on the highway, I looked over my shoulder, and started to merge- traffic was moving fine but as I turned my head back around my lane came to a stop and I rear ended this woman.

Before people start commenting saying I’m a terrible driver and inform me how it’s not Tesla’s job to stop you, blah blah blah, I’m not looking for that. I am NOT blaming my car for anything and I am not stating it should have made everything all better- I am just curious why EAB didn’t kick in at all. Video below.


2019-11-08_08-16-11-front.mp4
 

derekmw

Member
Oct 3, 2016
623
892
San Diego, CA
Sorry that happened, such a crappy feeling. I'd be curious to know this too. I've had cases where I was paying attention and not even close to hitting the car in front (that was stopping but while switching to another lane) where the EAB kicked in so hard even the ABS kicked in braking to 'avoid' the possible accident.
 

ecarfan

Well-Known Member
Sep 21, 2013
19,198
13,848
San Mateo, CA
I revised the thread title so that it provides more information about the topic of discussion than simply “Collision”. Note that Tesla calls the feature “Automatic Emergency Braking” (AEB).
I am just curious why EAB didn’t kick in at all.
Have you checked your settings to confirm it is turned on? Go to Controls > Autopilot and make sure AEB is on, then tell us what the “Forward Collision Warning” is set to.

I watched your video. It appeared to me that the car did slow down before impact. Maybe I’m wrong about that. Did you apply the brake, or did the car do that automatically?

It is important to keep in mind that AEB will not prevent an impact. It is designed to reduce the speed at impact and thereby reduce the likelihood of severe injury. Now will AEB steer the car away from an obstacle.

So I’m wondering if AEB did in fact activate and slow the car before impact, or if you perhaps applied the brakes at the same time as the AEB did. Or are you saying that your car did not slow at all before impact?

Just trying to understand your situation.

4D5AFD24-4BF1-4ADF-BB4E-F42DAF5AE177.jpeg
 
Last edited:

St☰v☰

Member
Aug 27, 2019
787
529
SoCal/Texas
I may be wrong, but it's my understanding collision avoidance only works 100% in AP, FSD, and TACC. But In normal driving all I get is the car that's too close turns red and the warning goes off and EAB will slow you down but not necessarily stop you, at least that's been my understanding.
 
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P3dStealth

Member
Nov 12, 2019
916
990
USA
Sorry about your car but good job getting off the expressway after.. Most people tend to just stop in the expressway like the police are going to show up and make it a crime scene.

pics of damage?
 
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DirtyT3sla

Member
Apr 17, 2019
533
558
Holly
Uggh sorry to hear that. I've done something similar but at a much lower speed - look for oncoming traffic, and when you look the people ahead stop :l

And of course some ass in a pickup needs to fly past you both on the right. What an idiot.
 
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b9918

Member
Jul 17, 2019
9
17
Chicago
Here's some useful info including specific details from the manual on how it works and when it is deactivated. Good luck.
Collision Avoidance-Always on? | Tesla

Great link and OP, I think this may cover it based on your video:

Automatic Emergency Braking does not apply
the brakes, or stops applying the brakes, when:
• You turn the steering wheel sharply
 

Marcin411

Member
May 1, 2019
35
32
Minneapolis, MN
I may be wrong, but it's my understanding collision avoidance only works 100% in AP, FSD, and TACC. But In normal driving all I get is the car that's too close turns red and the warning goes off and EAB will slow you down but not necessarily stop you, at least that's been my understanding.

In my experience I have seen both the red car warning and actual vehicle applying the brakes but under different circumstances, I also never drive on AP. The only time I have experienced the vehicle actually apply the brakes is when the vehicle in front of me decelerates and I accelerate with about a car length or less in separation. I've had this happen about half a dozen times all within these parameters. The red car warning seems less consistent and I have not been able to narrow down the triggers for the warning with any consistency.
 

MXWing

Well-Known Member
Oct 13, 2016
7,300
17,937
USA
I revised the thread title so that it provides more information about the topic of discussion than simply “Collision”. Note that Tesla calls the feature “Automatic Emergency Braking” (AEB). Have you checked your settings to confirm it is turned on? Go to Controls > Autopilot and make sure AEB is on, then tell us what the “Forward Collision Warning” is set to.

I watched your video. It appeared to me that the car did slow down before impact. Maybe I’m wrong about that. Did you apply the brake, or did the car do that automatically?

It is important to keep in mind that AEB will not prevent an impact. It is designed to reduce the speed at impact and thereby reduce the likelihood of severe injury. Now will AEB steer the car away from an obstacle.

So I’m wondering if AEB did in fact activate and slow the car before impact, or if you perhaps applied the brakes at the same time as the AEB did. Or are you saying that your car did not slow at all before impact?

Just trying to understand your situation.

I agree and would ask the same questions.

Does any resource online FULLY understand how AEB works? I imagine if the driver's foot is on the accelerator, AEB would get overridden?

It's a a good demonstration that it probably makes sense to have TACC on even if not using autosteer. That would save a lot of grief here.

I am sorry for you @kaelandavis1 .
 
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ranova

Member
Apr 16, 2018
376
341
NorCal
honestly, this is why looking over the shoulders to change lanes/merge is dangerous. Anything can happen in a split second with something in front of you. This is why I went with convex side mirrors so I could see from the side of my car to my blind spots. Now Tesla needs to integrate the side repeaters to pop up a live view when you use your turn signals like Kia, Hyundai, Honda, etc.
 

ecarfan

Well-Known Member
Sep 21, 2013
19,198
13,848
San Mateo, CA
Does any resource online FULLY understand how AEB works?
My answer to that would be categorically “no”. There is, however, a huge amount of speculation online.
I imagine if the driver's foot is on the accelerator, AEB would get overridden?
My guess would be “yes”. But I could be wrong.

So in the situation described by the OP, we don’t know if he was pressing on the accelerator just before impact, which could conceivably have overridden AEB.

And human memory being what it is, it is possible he might not accurately recall if he was pressing on the accelerator. Humans do a lot of things subconsciously, things that do not get stored in their short term memory.

@kaelandavis1 I am not accusing you of doing anything wrong. Just describing a possible scenario where AEB might not have been activated. When I look at your video it appears that when the brakes lights of the car in front of you come on you could have been accelerating slightly. But I still think that just after those brake lights came on your car slowed just a bit. Whether that was you initiating the slowing or AEB I have no way of determining.

As @MXWing noted, if TACC had been engaged it very likely would have slowed your car sufficiently rapidly to avoid the collision. I have been in many situations where with TACC on and the car it was tracking in front of me suddenly slowed dramatically, my car slowed as well and there was no collision.
 
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Shemp

Supporting Member
Sep 20, 2019
63
48
Detroit
Sorry about your accident.... Pure speculation here, but could it possibly be because the car was not pointed squarely at the car in front of you? I'm guessing the software may not use EAB when the car may avoid the obsticle.

I had active cruise control in my Taurus SHO, and it was pretty good, but it would sometimes annoyingly slow the car or activate a collision warning alert in similar situations where I was passing a turning car or changing lanes and not close to an actual collision as I was going around the car. I'm guessing Tesla may have attempted to smooth that out a bit, although in the process allowing corner hits like yours.

Again, I have no knowlege of the system, this is just speculation on my part.
 

S4WRXTTCS

Well-Known Member
May 3, 2015
5,367
6,069
Snohomish, WA
The problem with AEB is it's really only a crash mitigation system. Sure it can at times prevent a collision, but by design it's a crash mitigation system.

The irony is you crashed into a Subaru, and Subaru has a better AEB system (not my claim, but results from independent testing like the IIHS).

What firmware version were you on? I'm asking because I'm wondering if the latest update played any role in it.

For future reference I'd use TACC in a situation like that. The reason is I want a double set of eyes, and AEB is simply not a double set of eyes. With TACC you have a much higher likelihood of false braking, but less likely that it would fail to stop. Now TACC might fail to stop for a stopped object like if the car in front of you suddenly veered over for a stopped car in front of it.
 
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MXWing

Well-Known Member
Oct 13, 2016
7,300
17,937
USA
In this particular situation, TACC would have saved the day. As the forward car slowed and your following distance decreased, the Tesla would have deaccelerated sharply as well.

TACC (at this time) however, is going to crash you into an immobile object which includes cars that are stopped. This just means you have look down the horizon or when coming up to a stop car situation.
 

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