Automatic Emergency Braking

[S4WRXTTCS]

Currently on Arstechnica there is a 7-8 page thread talking about a recent accident involving a Model S that rear ended another vehicle while driving down I5. The driver didn't realize that she had turned off the adaptive cruise control, and assumed that the car would stop. The car didn't stop because the driver had disabled TACC by braking.

My initial conclusion that while it was the drivers fault it was also a UI issue because the car was in a different mode of operation than what the driver expected.

In mulling it over the last day and half I've come to two conclusions that are related.

1.) There seems to be a lot of confusion among everyone in that thread over what constitutes Automatic Emergency braking. There were lots of assumptions that the automatic emergency braking should have stopped the car regardless of whether the driver hit the brakes or not. But, they didn't seem to realize that the Emergency braking on the Tesla is only designed to reduce the severity of the crash. It's designed to only activate when a crash is determined to be unavoidable. At least that's what the user manual states. In researching it a bit I realized the entire industry didn't have a standard as to what emergency braking was. The Insurance institute's best rating doesn't even require a car to stop all the way. It's simply a rating of cars that have automatic braking systems that can reduce the severity of a crash. Yet, lots of companies use the verbiage of accident avoidance.

2.) That adaptive cruise control systems are inherently incompatible with automatic emergency braking systems that only offer crash mitigation. The problem is the mode of operation for TACC allows a driver to comfortably expect the car to stop for upcoming traffic. Over thousands of miles the driver gains a good level of confidence in it, and there is little concern about it stopping. But, if the user has accidentally disabled the TACC it means the driver is unknowingly relying solely on the emergency braking to save his/her bacon. But, the emergency braking is only designed to reduce the severity. It's also designed to be easily disabled by hitting and releasing the brakes.

 

[S4WRXTTCS]

I apologize for the typo's and the grammar. I thought I could edit it after I posted it, but apparently not.

 

[TrevTremaine]

It's an interesting case to say the least. I'm not sure I agree with your conclusions completely, but I believe fully trusting any system at this point is wrong (especially at highway speeds) - drivers should consider it as "beta in production". I disagree that there should be a disconnect between collision mitigation and whether the driver chooses to use TACC or drive themselves - even if the driver does touch the brakes. Below is an article from CNN that looks at the situation from a 2013 perspective, but for the most part is still valid.

The best (and worst) crash avoidance technologies

The IIHS tests are here:

Crash avoidance features

Each accident case has it's own unique circumstances, although I can see that autonomous systems that solely rely on radar are more susceptible to "blind" collisions when it can't see beyond the car right in front of it. Even with a single camera there's a lot to be desired.

I'm unsure how well Infiniti's system works where it supposedly looks underneath the car ahead using radar, however, it seems that Subaru has gotten it "more right" than others with it's new gen Eyesight. It may be a factor using a combination of dual cameras and radar as Subaru does. The caveat is still dependent upon how fast the vehicle is going - highway speeds are currently too fast for the system to fully react. I would assume it would require interconnectivity between vehicles (a la Volvo's system) before highway speeds would become safer.

One thing I note from the IIHS is that it indicates a fairly significant difference between the S and the X over functionality crash avoidance features - I'm not sure if the refresh takes all of this into account.

 

[S4WRXTTCS]

What I don't like about the current implementation is a driver is actually safer with TACC mode on than they are with TACC mode off.

When some perspective buyer watches a video of a Tesla braking to avoid an accident I don't know if it's clear to that buyer that the car was likely in TACC mode.

I wish Tesla would come out with a simulator/game so we could test out the various collision avoidance/mitigation systems. Where we could have TACC on and have TACC off. Right now all we have to go off of is the manual, and I don't know how true the manual is to what's on the car.

I'll have to read the Model X manual to see if it conveys any differences between the functionality of my Model S and it.

I do think Tesla will improve this and I imagine it will happen when they introduce the system with the extra frontal camera's within the next 3-6 months (based on rumors that I've read about on this site).

 

[Az_Rael]

Here is the article at Ars: Another driver says Tesla’s autopilot failed to brake; Tesla says otherwise

So Tesla says the tapping the brake pedal DISABLES the auto emergency braking. That it not how I would expect that system to work at all.

I would still want AEB even if I was already on the brakes. What if I am not pushing them hard enough if the car in front decelerates rapidly? I would want the computer, who can recognize that faster than me, to increase the pressure on the brakes even while I am still on them. False alarms coud be cancelled with the throttle pedal.

From the release notes:
Automatic Emergency Braking Automatic Emergency Braking — a new Collision Avoidance Assist feature — is designed to automatically engage the brakes to reduce the impact of an unavoidable frontal collision. Automatic Emergency Braking will stop applying the brakes when you press the accelerator pedal, press the brake pedal, or sharply turn the steering wheel. Automatic Emergency Braking is enabled by default. You can temporarily disable this feature via the AUTOMATIC EMERGENCY BRAKING setting in Controls > Settings > Driver Assistance > COLLISION AVOIDANCE ASSIST. Automatic Emergency Braking will re-enable when you next drive. Note: Automatic Emergency Braking operates when you are driving at speeds between 5 mph (8 km/h) and 85 mph (140 km/h).

 

[robby]

So Tesla says the tapping the brake pedal DISABLES the auto emergency braking. That it not how I would expect that system to work at all.

I would still want AEB even if I was already on the brakes. What if I am not pushing them hard enough if the car in front decelerates rapidly? I would want the computer, who can recognize that faster than me, to increase the pressure on the brakes even while I am still on them.

The rationale, FWIW, is that AEB is designed to brake before you would react. If you're already on the brakes, you've presumably already reacted and are in control.

There are some situations where you might be lightly on a brake and need more urgent, heavy breaking -- AEB is compromised in this situation and the tradeoff is that it doesn't take you quite as long to react because your foot's already in place. There might be a better, no-compromise system for this situation but I'm not sure what it would be. I think relying on the accelerator to deactivate AEB would be a huge mistake -- you never want people to be hitting the accelerator in a braking situation.

 

[Az_Rael]

I think relying on the accelerator to deactivate AEB would be a huge mistake -- you never want people to be hitting the accelerator in a braking situation.

I wouldn't want it disengaged in a braking scenario ever. Disengaging via the throttle would be if the system falsely detected a object ahead of me that wasn't actually there (I have heard metal covers across roads in construction zones can sometimes freak the car out). In that scenario, I would just tap the accelerator to override and drive on as usual.

 

[S4WRXTTCS]

The AEB system has to have the ability to be deactivated with the throttle due not just to the possibility of false positives, but also during moments of evasive action.

You have to return control to the driver as quickly as possible when he/she takes over.

In that Ars thread it seemed to me that people had greatly exaggerated ideas of what the AEB system was capable of. Where they assumed it was being de-activated by the driver braking, but by the time it engages the driver was already doing maximum braking (at least that what the driver claimed). In that scenario the AEB system couldn't have done anything. My impression of the system is it will really only come to play in situations where the driver is completely unaware of the impending collision. Like if a pedestrian crossed path with the car and the driver didn't see them. The car will automatically brake to reduce the speed of the collision, but the collision will still happen (unless what you're about to hit gets out of the way).

 

[Az_Rael]

For reference, here is how a couple of other manufacturers do it:

GM:
Applies emergency braking even if you are on the brakes to increase braking force as needed. System is disabled only using accelerator pedal.


Acura:
Has 3 stages of automatic braking that involve lots of beeping and seatbelt tightening. Doesn't appear system can be disabled by manually applying brakes (there is a button for disabling it)

 

[Az_Rael]

by the time it engages the driver was already doing maximum braking

Except a very large percentage of the population has zero idea was "maximum braking" actually feels like or how hard you have to be pressing to be applying it. So I doubt she was applying maximum braking at the time. The AEB system could have helped in that situation, as it WOULD apply maximum braking, and it would do it faster than the driver


And it IS completely disabled on a Tesla as soon as you touch the brake pedal. That is the problem, I think. I would rather it stays on and continues to provide assistance.

 

[TrevTremaine]

For reference, here is how a couple of other manufacturers do it:

GM:
Applies emergency braking even if you are on the brakes to increase braking force as needed. System is disabled only using accelerator pedal.
View attachment 176693 View attachment 176694

Acura:
Has 3 stages of automatic braking that involve lots of beeping and seatbelt tightening. Doesn't appear system can be disabled by manually applying brakes (there is a button for disabling it)
View attachment 176703 View attachment 176702 View attachment 176701 View attachment 176700 View attachment 176699 View attachment 176698 View attachment 176697

Subaru continues to apply brakes even if one has their foot on the accelerator. You literally can't drive it into an obstacle if your speed is below 19 mph (I think that's the limit). I'm not so sure if it does apply the brakes any harder if one is already braking.

We Try Out Subaru’s EyeSight Collision-Avoidance Tech

 

[S4WRXTTCS]

Except a very large percentage of the population has zero idea was "maximum braking" actually feels like or how hard you have to be pressing to be applying it. So I doubt she was applying maximum braking at the time. The AEB system could have helped in that situation, as it WOULD apply maximum braking, and it would do it faster than the driver


And it IS completely disabled on a Tesla as soon as you touch the brake pedal. That is the problem, I think. I would rather it stays on and continues to provide assistance.

That's true about a large percentage of the population having no idea what maximum braking feels likes. But, I question whether the Automatic braking system in the Tesla is even capable of maximum braking. I'll have to look that up since I remembering reading something that said it wasn't. In my experience with it TACC seems pretty capable of hard braking, but I've never tried to see just how hard it could brake. I don't want to be the guy that gets into an accident with a Tesla because he was testing something even though it's in my nature to want to test things to their limits.

For me personally I'd rather have a passive AEB system that ONLY boosted the brakes to make them more effective, but didn't automatically apply the brakes. I don't like the idea of having a computer that could suddenly hit the brakes with that much force due to a false positive. False positives do happen, but luckily I haven't experienced it. I thought I was going to a few weeks ago when I drove through a huge mess of playing hards. I turned off TACC and put my foot on the throttle to push through any AEB action, but thankfully nothing happened.

 

[marcon]

The problem with the emergency breaking is that it doesn't fail safe. It doesn't seem to have a trivial solution, though. Especially as there were some reports of false positives of the emergency braking system on this forum, too, when autopilot came out.

Even an severe acoustic warning, only activated in an emergency situation as this one was, might actually confuse more than help.

It is a fundamental problem of trust. When TACC is expected to hit the breaks, and usually does this rather late, you then have to add at least a second of total reaction time to the point, when it would usually initiate.
When you have people driving into rivers, because their navigation system told them so, you will have people with total trust in their car automatically breaking, no matter what they themselves do, including deactivating TACC by mistake.

 

[S4WRXTTCS]

Subaru continues to apply brakes even if one has their foot on the accelerator. You literally can't drive it into an obstacle if your speed is below 19 mph (I think that's the limit). I'm not so sure if it does apply the brakes any harder if one is already braking.

We Try Out Subaru’s EyeSight Collision-Avoidance Tech

How does someone deal with false positives then?

A friend of mine has a Subaru with the EyeSight system (the system in 2015 models) and he claims that sometimes during adaptive cruise control driving that it will mistake a shadow for an object and slow down.

Maybe for AEB it's less prone to false positives. But, I do like the fact that on the Subaru system it does clearly state that it can come to a complete stop when the closing speed is 19mph or less. Where the Tesla AEB system only mentions reducing speed. So I'm not sure if there is much point in having it not disable when the driver removes the brakes. It likely wouldn't happen until after the collision happened anyways.

The fun thing about comparing the Tesla to the Subaru is both systems use MobileEye technology. The difference in the Subaru is it has two camera's where the existing Tesla system is one camera plus the radar. The next gen Autopilot will have more than one frontal camera, and I'm sure the Model 3 will too.

 

[Az_Rael]

Ok,so I read up some on the technologies. Tesla's system is missing DBS, which is dynamic brake support. That is the system that supplements a drivers actions once braking has already been applied. Other manufacturers do implement it, so Tesla is a bit behind the curve on this front.

Interestingly, the NHSTA is proposing including ratings of AEB systems in their 5-star crash ratings in the future. They will actually test the systems ability to detect objects and reduce crash velocities. Pretty cool stuff, really
https://www.gpo.gov/fdsys/pkg/FR-2015-12-16/pdf/2015-31323.pdf

 

[zambono]

Currently on Arstechnica there is a 7-8 page thread talking about a recent accident involving a Model S that rear ended another vehicle while driving down I5. The driver didn't realize that she had turned off the adaptive cruise control, and assumed that the car would stop. The car didn't stop because the driver had disabled TACC by braking.

My initial conclusion that while it was the drivers fault it was also a UI issue because the car was in a different mode of operation than what the driver expected.

In mulling it over the last day and half I've come to two conclusions that are related.

1.) There seems to be a lot of confusion among everyone in that thread over what constitutes Automatic Emergency braking. There were lots of assumptions that the automatic emergency braking should have stopped the car regardless of whether the driver hit the brakes or not. But, they didn't seem to realize that the Emergency braking on the Tesla is only designed to reduce the severity of the crash. It's designed to only activate when a crash is determined to be unavoidable. At least that's what the user manual states. In researching it a bit I realized the entire industry didn't have a standard as to what emergency braking was. The Insurance institute's best rating doesn't even require a car to stop all the way. It's simply a rating of cars that have automatic braking systems that can reduce the severity of a crash. Yet, lots of companies use the verbiage of accident avoidance.

2.) That adaptive cruise control systems are inherently incompatible with automatic emergency braking systems that only offer crash mitigation. The problem is the mode of operation for TACC allows a driver to comfortably expect the car to stop for upcoming traffic. Over thousands of miles the driver gains a good level of confidence in it, and there is little concern about it stopping. But, if the user has accidentally disabled the TACC it means the driver is unknowingly relying solely on the emergency braking to save his/her bacon. But, the emergency braking is only designed to reduce the severity. It's also designed to be easily disabled by hitting and releasing the brakes.

Emergency braking needs to be more aggressive and stop completely if needed.

 

[zambono]

For reference, here is how a couple of other manufacturers do it:

GM:
Applies emergency braking even if you are on the brakes to increase braking force as needed. System is disabled only using accelerator pedal.
View attachment 176693 View attachment 176694

Acura:
Has 3 stages of automatic braking that involve lots of beeping and seatbelt tightening. Doesn't appear system can be disabled by manually applying brakes (there is a button for disabling it)
View attachment 176703 View attachment 176702 View attachment 176701 View attachment 176700 View attachment 176699 View attachment 176698 View attachment 176697

Acura system please

 

[Ulmo]

The rationale, FWIW, is that AEB is designed to brake before you would react. If you're already on the brakes, you've presumably already reacted and are in control.

There are some situations where you might be lightly on a brake and need more urgent, heavy breaking -- AEB is compromised in this situation and the tradeoff is that it doesn't take you quite as long to react because your foot's already in place. There might be a better, no-compromise system for this situation but I'm not sure what it would be. I think relying on the accelerator to deactivate AEB would be a huge mistake -- you never want people to be hitting the accelerator in a braking situation.

What if there's a disagreement? Such as, the car thinks you'd like to avoid running over something, but you really need to, such as a large pack of lions or monkeys ready to attack you, after you stopped 100 feet before to analyze options, but realized there's no way to get off the road, turn around, or otherwise avoid engaging them, and you see them look violent toward you and start to approach. In a car without such "features" this would allow you to survive by continuing on, but with the "features" there needs to be a way to override.

 

[chillaban]

FWIW, a lot of the information is out-of-date in the posted manual. In Firmware 8.0, Tesla did adjust AEB to amplify user braking if the user brakes during a FCW alert, which seems to be a lot of what people want.

As far as multistage brake warning: It can get extremely annoying and unsafe extremely quick. My previous Audi had a multi-stage brake pulsing AEB system, and I've had it accidentally go off a few times when following a car at a U-turn where the radar and camera mis-predicted the front car's trajectory and assumed I was going to hit it. A sudden brake jolt threw me against my seat belt, gave me a nice 20 inch red rash, knocked the wind out of me, and nearly caused a chain collision behind me before I could catch my breath and take over control again.

For those wanting more protection, the FCW "early" option I've found starts alerting around the same time Audi's system would've started alerting. The "medium" option cuts down on false alerts but it also reduces your reaction time when an alert happens.

I think for most people, what they really want is a more proactive FCW than a more aggressive AEB. AEB is designed as a last ditch effort to reduce the severity of a collision. Having the car more proactively slam on the brakes is a million times worse than the discomfort of the "AP2 overpass braking" incidents that people are being drama queens about. If you don't believe me, be a passenger, close your eyes, and ask the driver to suddenly slam on the brakes without telling you when it's going to happen.