Model X v8.0 Autopilot rear-end collision

[onethumb]

I was driving northbound on I-280 in Northern California towards San Francisco with Autopilot fully engaged (speed and steering) in my wife's X. I had my hands on the wheel, was paying attention, and had my wife with me in the passenger seat. We were in the left-most lane, going ~70mph with the flow of traffic.

All of a sudden, the early collision warning started beeping at me and had correctly deduced, faster than I had, that the cars ahead of me were braking hard. For a split second, I wondered if I should let the Autopilot solve the problem, but it didn't feel like it was braking hard at all, and I just wasn't ready to trust it for something like this. As I took over and stomped on the brakes as hard as I could, my first thought was how surprised I was that there was a noticeable increase in the braking effort as soon as I took over.

As we were slowing down rapidly, I watched the two cars in front of me collide. For a split second it looked like we might brake in time, but alas, we did collide with the rear of the 2nd car. It was pretty light, I didn't even see any paint transfer between the two cars, my guess would be maybe 5mph?

No one was injured, but I have to admit, I was very surprised and it's shaken both my wife and I's faith in Autopilot and the Automatic Emergency Braking System (AEBS).

The early warning system did catch the accident occurring faster than I did, so in the end, the Tesla certainly helped mitigate the damage and keep everyone safer, for which I'm grateful. But at the same time, this seems like exactly the type of collision they're designed to avoid, and one of the major reasons we bought new Teslas in the first place.

After the accident, I checked my wife's settings, and saw that she was using more aggressive settings (2 on following distance, Medium on collision warning) on her car than I use on mine (5 on following distance, Early on collision warning), but I would still think those settings must be designed to work, or else they wouldn't have them configurable like that to begin with?

I've emailed Tesla about seeing if they can analyze the data and give us any feedback or at the very least feed it into their machine learning, but that was nearly two weeks ago and I still haven't heard back.

Has anyone else had any similar experiences? Has anyone managed to get Tesla to look into a report like this? If so, how?

 

[outie]

Sorry to hear that. Driving 70mph with a following setting of 2 is too just close to act for both you and the car. The car does not take braking distance into consideration.

 

[hollywood]

I was told that the collision warning should be set consistent with your driving speeds in balance to your separation distance. Especially important if only maintaining 2 car lengths.
Early - over 65
Medium 40-65
High - under 40

 

[vandacca]

Wow. Glad to hear that everyone walked away safely. I suspect that if you had follow-distance set to 5 and Early Collision warning, you probably would have avoided the low-speed bump.

Did you get any acknowledgement response from Tesla, indicating that they got your Email? If not, then I would call the support line, just to make sure that your Email wasn't lost in the shuffle. Even call your SC if necessary.

I'm not at the point yet where I fully trust AutoPilot, and only seem to use it when in the carpool lane and/or during light traffic. I'm trying to force myself to use it in stop-n-go traffic, but I haven't had much opportunity yet.

My biggest concern is that AutoPilot will disengage as soon as you take over (eg. steering or braking) and in that small moment of confusion, a human mistake could make the situation worse (rather than just leaving AutoPilot to make the decisions). I'm still in the "learning" stages of using AutoPilot.

 

[travwill]

I recall in the owners guide and previous discussion that collision avoidance in our Teslas is design to slow slow/minimize the impact of a rear collision but not fully stop the car. It will slow you down up to 25 mph from where you were earlier than you can but you still have to brake hard for the full stop.

 

[chillaban]

TACC/AP is not designed to follow at a distance impervious to accidents regardless of situation, unfortunately. That would essentially mean 200+ feet of following distance at highway speeds (150ft or so for stopping distance at emergency braking speeds + 50ft for a 0.5s reaction time at 60mph)

In CA, as you well know, you might as well put a sign out in front of the car that says "YOU ARE CORDIALLY INVITED TO CUT IN FRONT OF ME"


The most hazardous situation for TACC/AP is when the person in front of you rear-ends the 2nd person in front of you, because your following distance chosen is almost purely dependent on the person in front of you being a good driver. 8.0 improves that a bit, which is why you got a bit more advance notice from the collision warning that there was going to be an accident.


In my experience, any following distance below 4-5 is technically tailgating and puts you below the recommended following distance guidelines, which means you run some risk of an accident. The fact that you had a minor collision without substantial body damage meant AEB did do its job in minimizing the impact compared to if you were driving yourself. As you said -- you were paying full attention and it wasn't until after the collision alert that you realized indeed there was an impending accident. If anything, having AP/TACC/AEB allowed you to react better to this situation than without.



But as an aside, sorry about the accident. I see this kind of collision happen at least once a month commuting in the South Bay



EDIT: You should definitely reach out to Tesla (e.g. ServiceHelpNA or the phone number) to share your story and see if there's any logs they could pull. But I wouldn't try to push a narrative where you imply blame on Autopilot/Tesla for the collision, which is much less likely to be productive.

 

[Ferrett]

I had the same experience, and had to take over. Luckily, I did not hit the front car (ONLY BECAUSE I TOOK OVER). The braking during emergencies for auto-pilot is definitely NOT aggressive and NOT SUFFICIENT.

BTW onethumb, nice smugmug portrait. I may have worked with you before?

 

[Saghost]

If the car in front of you hits something, it stops almost instantly. That takes away the stopping distance the car is expecting and counting on.

That's why accidents in heavy traffic almost always turn into multicar pileups - very few people leave themselves anywhere near enough time to react and stop.

 

[MP3Mike]

No one was injured, but I have to admit, I was very surprised and it's shaken both my wife and I's faith in Autopilot and the Automatic Emergency Braking System (AEBS).

The early warning system did catch the accident occurring faster than I did, so in the end, the Tesla certainly helped mitigate the damage and keep everyone safer, for which I'm grateful. But at the same time, this seems like exactly the type of collision they're designed to avoid, and one of the major reasons we bought new Teslas in the first place.

Where does Tesla say they have a collision avoidance system? I wish people would stop claiming that they do, as they don't. (Not yet anyhow.) Automatic Emergency Braking, AEB, is only designed to reduce the impact of a collision that the system has determined is unavoidable. (i.e. it is a collision mitigation system.)

On the other hand TACC shouldn't be involved in a collision unless you were following too close and things happen too quickly. Which is what it sounds like happened.

 

[X Fan]

Don't have Cali cutters to deal but always +7 on highway for me.

In bumper to bumper will tune down but never on interstates.

Sorry a bout your accident but glad everyone is ok.

 

[S4WRXTTCS]

AEB is a crash mitigation system so it won't stop you completely. But, at least unlike versions before 8.0 it will implement maximum braking once it determines a collision is imminent. Are you on firmware 8.0? Firmware 8.0 should also give you more warning for this as it can track the car two cars ahead.

I see the REAL problem being the way people in California drive. They simply do not allow people to proper following distances.

I wish Tesla would have an early warning system when the Google Nav see's the traffic suddenly coming to a halt a mile or two away. That way even in the hell hole that is Cali you could prevent this kind of thing most of the time.

My only real concern about TACC is that half second delay or so between the time a human spots a quick slow down, and then decides to take over. Where they're wondering if they should take over or not versus immediately taking over.

 

[thegruf]

AEB is a crash mitigation system so it won't stop you completely. But, at least unlike versions before 8.0 it will implement maximum braking once it determines a collision is imminent. Are you on firmware 8.0? Firmware 8.0 should also give you more warning for this as it can track the car two cars ahead.

I see the REAL problem being the way people in California drive. They simply do not allow people to proper following distances.

I wish Tesla would have an early warning system when the Google Nav see's the traffic suddenly coming to a halt a mile or two away. That way even in the hell hole that is Cali you could prevent this kind of thing most of the time.

My only real concern about TACC is that half second delay or so between the time a human spots a quick slow down, and then decides to take over. Where they're wondering if they should take over or not versus immediately taking over.

Yikes - I need to rtfm then.
The fact I even need to think about doing this suggests I and presumably many others are not clearly aware of the detail of how these systems operate or indeed their operation has been changed.
Arguably clarity of system behaviour is something Tesla should address.

I thought that AEB implemented braking but not at 100% but sufficient to reduce speed by 25-30mph, alerting the driver to take over aubibly and through the unexpected deceleration in the process.

I thought the change in v8 was that instead of AEB being disabled by the driver taking over braking (and possibly therefore not acting if the driver tapped the brakes and the released which in turn seemed possibly to be the cause of some rear enders previously reported).
However in v8 I also belived that AEB in v8 now exaggerated the drivers braking input once applied, reinforcing the stopping effort.

From the OPs post this would seem to be in line with what happened. AEB acted, alerted the driver, the driver took over and braked and the car in turn applied maximum braking, almost but not quite preventing a collision.
Actually it seems to me that AEB did a good job and may well have prevented a much more serious impact.

There also seems to be some confusion between AP follow distance and AEB.
I believe they work largely independently. AEB is more of an emergency measure whereas AP is constantly trying to maintain a gap.

fwiw I always have AEB set to early and it works well for me, so much so that this is the only setting I would recommend to anybody. On the odd occasion it does beep I have more than sufficient time to react although invariably I am on the point of reacting anyway.

The AP setting 1-7, I believe is set in time not distance (maybe not strictly true at low speeds), #2 seems to be about 2 seconds. In hectic traffic I may use #2 to minimize cut ins but I would be on high alert; more relaxing driving I would typically use #3-5

 

[chillaban]

I see the REAL problem being the way people in California drive. They simply do not allow people to proper following distances.

Bingo, 100% agreed. It's a 100% fact-of-life with how everyone drives in California. You can either do what is considered socially acceptable and end up accepting the nonzero risk of a traffic situation that you can't reasonably react to, or having a huge following distance and having swarms of angry drivers swerve around you then cut right back in front of you, which once again puts you at a risky following distance and furthermore exposes you to the nonzero risk of road rage / retaliation.

The AP setting 1-7, I believe is set in time not distance (maybe not strictly true at low speeds), #2 seems to be about 2 seconds. In hectic traffic I may use #2 to minimize cut ins but I would be on high alert; more relaxing driving I would typically use #3-5

Note that those following guidelines tend to work under the assumption that the car in front of you is not going to metaphorically hit a wall. Even with 5 seconds of following distance, if the person in front of you was about to plow into a standstill vehicle at full speed (and you could not see this about to happen), you'd likely still not have enough time to fully stop your car.

It's unfortunately just an inherent risk of driving in stop and go traffic, and as much a social problem as a technical and legal problem. The laws regarding lane changes in CA don't even require the driver making the lane change to ensure that they are leaving adequate following distance for the person in front and the person behind. Not to mention a law like that would be very impossible to enforce.



P.S. The optimistic way of looking at it: As a Tesla owner with AP, the mere fact that you get a beep from your car that it thinks an accident is about to occur already puts you in the minority of the maybe 25% (or less) of driving elite that have a car new enough and equipped enough to have collision mitigation.

 

[S4WRXTTCS]

I thought the change in v8 was that instead of AEB being disabled by the driver taking over braking (and possibly therefore not acting if the driver tapped the brakes and the released which in turn seemed possibly to be the cause of some rear enders previously reported).
However in v8 I also belived that AEB in v8 now exaggerated the drivers braking input once applied, reinforcing the stopping effort.

From the OPs post this would seem to be in line with what happened. AEB acted, alerted the driver, the driver took over and braked and the car in turn applied maximum braking, almost but not quite preventing a collision.
Actually it seems to me that AEB did a good job and may well have prevented a much more serious impact.

There also seems to be some confusion between AP follow distance and AEB.
I believe they work largely independently. AEB is more of an emergency measure whereas AP is constantly trying to maintain a gap.

fwiw I always have AEB set to early and it works well for me, so much so that this is the only setting I would recommend to anybody. On the odd occasion it does beep I have more than sufficient time to react although invariably I am on the point of reacting anyway.

The AP setting 1-7, I believe is set in time not distance (maybe not strictly true at low speeds), #2 seems to be about 2 seconds. In hectic traffic I may use #2 to minimize cut ins but I would be on high alert; more relaxing driving I would typically use #3-5

That's all correct as far as the AEB changes are concerned.

I wasn't sure what to apply to the OP since there isn't a confirmation of which firmware version they had. I'm a little surprised it would happen with 8.0 given the FCW can look two cars ahead. But, maybe it was just all so close in that it didn't help much.

With AEB you can't change the setting. You can disable it temporarily, but other than that you can't change anything about it. The AEB is completely separate from TACC/AP or FCW. Nothing about those systems impact the AEB. The AEB is like the car going "Oh crap I'm going to die, and then braking enough to slow down by 25mph.

For completeness in the manual previous to 8.0 it used to say it would cut down the speed by 25mph, but on the new 8.0 manual it doesn't give an exact speed.

 

[Scrith]

Yes, I've had two similar incidents in my X on 101 on the SF Bay peninsula. I wasn't using autopilot on either occasion, but in both cases there was a sudden slowdown by vehicles directly in front of me, the early warning systems started beeping, and I hit the brake as hard as I could, but the vehicle didn't slow as much as I expected (based on how it slows in non-emergency situations in my experience based on 6 months of driving it). But the opposite happened in my case...I became convinced it wouldn't stop in time, then the emergency systems seemed to make it brake even harder, and I stopped just in time.

In both cases, afterwards I was left wondering whether my braking was compromised because perhaps my big feet (US size 16) were somehow hitting the accelerator by accident in addition to the brake, but I'm not 100% sure that was what was happening (it has never caused a problem for me in other vehicles in 30 years of driving, but I am still wondering what happened so I'm speculating to find an explanation). I wrote an e-mail to Tesla (which was acknowledged and forwarded to some department) suggesting that they modify the software to disable the accelerator when the brake is being pressed, which should be a trivial code change, but never heard back from them.

 

[Electroman]

it would seem that V8 did not give any extra capabilities. Any improvements one may have noticed is just placebo effect.

 

[MP3Mike]

I wrote an e-mail to Tesla (which was acknowledged and forwarded to some department) suggesting that they modify the software to disable the accelerator when the brake is being pressed, which should be a trivial code change, but never heard back from them.

I'm pretty sure that is already the case. You should try it in a parking lot or a safe section of road to see what happens.

 

[chillaban]

I'm pretty sure that is already the case. You should try it in a parking lot or a safe section of road to see what happens.

It is indeed already the case. You get a triple-beep then "Both Pedals Pressed", and the brake overrides the accelerator.

(P.S. In the heightened adrenaline of an emergency, humans are quite unreliable data recorders for what objectively happened. It's in our biology)

 

[ecarfan]

After the accident, I checked my wife's settings, and saw that she was using more aggressive settings (2 on following distance, Medium on collision warning) on her car than I use on mine (5 on following distance, Early on collision warning), but I would still think those settings must be designed to work, or else they wouldn't have them configurable like that to begin with?

Tesla clearly does not guarantee that AP and AEB will prevent contact with other cars during an emergency no matter what your AP settings are. Based on my understanding of your description of the event AP warned you of a possible collision and AEB kicked in and did what it is advertised to do: reduce the speed of impact if a collision is unavoidable.

You seem to be under the impression that no matter what you do or what surrounding cars do a Tesla on AP will avoid a collision. That is not the case.

In my opinion a TACC setting of 2 does not allow enough following distance. That seems self-evident to me. Tesla leaves it up to the judgement of the driver. Use your judgement and think about the distances required to come to a stop. Even a setting of 5 is too low in my opinion. When I drive an AP-equipped Tesla I always set it to 7.

 

[ItsNotAboutTheMoney]

To add to what others are saying: AEB _will_ _not_ prevent contact. In my opinion it _should_ _not_ try to prevent contact when braking from higher speeds. To avoid contact means more rapid braking, and more rapid braking increases the chances of a rear-end collision. Since AP1 is not able to process the rear view, the safest action should be to have a limit on braking force and allow the car to hit the car in front at a low speed. If all cars did that in dense traffic, there would be a chain of safe, low-speed collisions, up to a point after which all cars down the chain would be able to stop without collision.