Automatic Emergency Braking: Not Working. Why?

[SciFriGuy]

The Tesla manual says:
Active Safety Features
All Tesla cars made since October 2016 come standard with advanced active safety features for elevated protection at all times. These features are made possible by our Autopilot hardware system and include:

• Automatic Emergency Braking: Detects cars or obstacles that the car may impact and applies the brakes accordingly

I have a 2018 Tesla, AWD, Autopilot but not FAP. If Automatic Emergency Braking comes standard, why does my car not automatically brake when approaching a stopped car at a red light at 30mph? Am I not configured correctly? The switch is "on" in control panel.

The only time it automatically brakes is when cruise control is on.

 

[Leopold Stotch]

Emergency braking will only activate if car thinks collision is unavoidable. So if you did not get into an accident, there was no need for emergency braking.

 

[SciFriGuy]

Leopold, what you're saying is that emergency braking will not prevent a collision since if only activates when a collision is "unavoidable." It can't make an unavoidable collision avoidable.

 

[AlanSubie4Life]

Leopold, what you're saying is that emergency braking will not prevent a collision since if only activates when a collision is "unavoidable." It can't make an unavoidable collision avoidable.

This was discussed elsewhere. First, AEB is not 100% effective. It is a collision mitigation mechanism, not a collision avoidance mechanism. Sometimes it may not even mitigate the collision (when it fails to detect an imminent collision for whatever reason).

It makes a huge difference if you hit someone at 30mph, vs. 10mph (it is 9 times better at 10mph). So even some braking is good.

It WILL sometimes work, but remember it does not have to worry about human reaction times when applying the brakes. It knows how long it takes to stop (assumes ideal dry conditions I suppose) and will wait until the very last moment necessary to apply the brakes.

I would read the entire section in the manual. There are a LOT of caveats.

This is the previously referenced article:

Automated-Emergency-Braking Systems Don't Always Work - Test Results

I don't think there is any feature called FAP. I know, you meant EAP...

FCW should alert prior to AEB, so set that to maximum sensitivity. I don't recommend testing it specifically; eventually a situation will arise where the warning will trigger in your normal driving. In theory, if FCW goes off, the car SHOULD soon thereafter emergency brake to mitigate (possibly not avoid) the collision. Do not test it.

---
Regarding the cruise control braking...as the article above describes, it will brake for TRACKED vehicles (I don't mean tanks...). Untracked vehicles, not so much. Please do not expect it to brake for untracked vehicles (also don't expect it to brake for tracked vehicles...). These tracked vehicles are indicated on the screen as a darker vehicle (I think). As indicated in the manual, there are also a lot of caveats with respect to TACC and when it will be effective at tracking the leading vehicle's speed.

These features are all Advanced Driver Assistance features, and you should not expect them to avoid any collisions. They are meant to cover SOME situations where you are somehow surprised/distracted/incapacitated (possibly through no clear fault of your own). These situations are one of the most common causes of accidents and injury/fatalities, and these features when properly implemented can drive down those accident & property damage rates. There are balancing effects which drive up rates, however, when people begin to rely too much on the systems (avoiding this is part of "proper implementation").

 

[SciFriGuy]

AlanSubie4Life Thanks for that cogent and detailed reply.

 

[ewoodrick]

In short, you chickened out before it engaged. The braking distance at 60 is about 130ft. So at 30mph it is going to be less. Measure how long 60ft is and I suspect that you chickened out possibly before 130ft.
And as other has mentioned, it's intent is not to circumvent fender benders, it's goal is to circumvent fatalities.

 

[Silicon Desert]

In short, you chickened out before it engaged. The braking distance at 60 is about 130ft. So at 30mph it is going to be less. Measure how long 60ft is and I suspect that you chickened out possibly before 130ft.
And as other has mentioned, it's intent is not to circumvent fender benders, it's goal is to circumvent fatalities.

I certainly agree with all that has been said thus far. My comment is that Tesla is often not very good at explaining things and usually ambiguous. With the statement of "Automatic Emergency Braking: Detects cars or obstacles that the car may impact and applies the brakes accordingly", I can see how the OP and other people might misunderstand to think the car is going to protect them "sooner" and more than it does.

In my 3 years of use, Fortunately, I have never experienced this mystery feature, but I have witnessed numerous occasions where it suddenly brakes for ghosts, trees, overpasses, and maybe even giant rain drops for all I know.

 

[Silicon Desert]

And as other has mentioned, it's intent is not to circumvent fender benders, it's goal is to circumvent fatalities.

Yup, but I wonder why there are several documented cases where the car runs into barriers and other objects, thus killing people. I like the statement that it helps to "mitigate" serious issues because that seems to be what it does. If the goal is to circumvent fatalities, then it isn't doing a very good job of it yet.

 

[AlanSubie4Life]

In short, you chickened out before it engaged. The braking distance at 60 is about 130ft. So at 30mph it is going to be less. Measure how long 60ft is and I suspect that you chickened out possibly before 130ft.
And as other has mentioned, it's intent is not to circumvent fender benders, it's goal is to circumvent fatalities.

Braking distance is 33ft or so from 30mph for MXM4.

With PS4S it is about 26ft from 30mph. (105ft from 60mph).

At half the initial velocity, takes half the time to stop and your average speed is half. So 1/4 the distance.

x = v^2/(2*a). Where a is the acceleration (deceleration), which would be the same for both speeds. PS4S have higher "a" than MXM4.

 

[SciFriGuy]

In short, you chickened out before it engaged. The braking distance at 60 is about 130ft. So at 30mph it is going to be less. Measure how long 60ft is and I suspect that you chickened out possibly before 130ft.
And as other has mentioned, it's intent is not to circumvent fender benders, it's goal is to circumvent fatalities.

If your saying "I chickened out" to avoid a collision, you're absolutely right. I gave up playing chicken in high school

 

[quikshifter]

My subaru with eyesight would warn and then hit the brakes and avoided collisions 100% of the time but I am not sure Tesla is the same.