AEB triggered by roadside car breakdown

[JC86]

interesting scenario today that I thought I'd share to see if anyone else has had a similar experience.

I was on the freeway headed to work with AP engaged in the right lane getting ready to exit when I noticed a a car and tow truck in the breakdown lane to my right.

I was curious as to how AP would react to this scenario so I left it on as we passed the car and tow truck.

AEB kicked in with the rapid three beeps and red light flashes on the IC, the car decelerated rapidly as I drove by the stopped car and then, as if nothing happened, re-accelerated as we passed them.

From what I can see, the tow truck and broken down car was close to but not on or over the lane line between us. AP still thought it was an obstacle and triggered AEB.

Not a big deal as I was ready to take over in any emergency but was still sort of surprised AEB kicked in and car decelerated rapidly. The only real threat would have been if I had a car following me too closely.

I'm constantly learning about the quirks and nuances of AP and this is just another case of that. Just thought I'd share.

 

[Science fan]

I think I might also slow down in such a situation, not entirely certain that a person would not be walking into harm's way from the other side of the truck. I also move over at least a half lane if there is a bicyclist in the bike lane. If there is no room, I slow down until there is room.

 

[jmsurpri]

With autopilot OFF and driving manually, I've had a collision avoidance alarm when there was a bike in the bike lane next to me that was slightly over the line.

 

[Max*]

Are you sure it was AEB and not FCW?

 

[Max*]

I think I might also slow down in such a situation

In some states it's required that you slow down or move over for a vehicle on the shoulder with flashing lights (police, tow truck, etc.)

 

[JC86]

Are you sure it was AEB and not FCW?

Aren't they the same thing?

 

[murphyS90D]

Required to slow way down and get out of the lane adjacent to the breakdown, if safely possible, in PA.

 

[Max*]

Aren't they the same thing?

No...

FCW = Forward Collision Warning. It's the red car that beeps on your IC.
AEB = Automatic Emergency Braking. Self explanatory, I think.

If AP is not engaged, and the car starts braking suddenly, it's not FCW, it's AEB. FCW doesn't slow the car, it's a warning.

When AP is engaged, TACC may have slowed the car down because it assumed something was in your lane and what you saw was a FCW message. Or it could have been AEB.

But no, they're not the same thing.

 

[JC86]

No...

FCW = Forward Collision Warning. It's the red car that beeps on your IC.
AEB = Automatic Emergency Braking. Self explanatory, I think.

If AP is not engaged, and the car starts braking suddenly, it's not FCW, it's AEB. FCW doesn't slow the car, it's a warning.

When AP is engaged, TACC may have slowed the car down because it assumed something was in your lane and what you saw was a FCW message. Or it could have been AEB.

But no, they're not the same thing.

Fair enough, thanks for the clarification. It's a rather nuanced differentiation.
I'm pretty sure it AEB because TACC is never as sudden and aggressive in its deceleration. In this particular instance, the FCW and AEB kicked in very aggressively to decelerate the car as I got near the tow truck. Although I think TACC did kick in after I passed the stopped car to my right.

 

[ecarfan]

In some states it's required that you slow down or move over for a vehicle on the shoulder with flashing lights (police, tow truck, etc.)

In California, which is where the OP appears to live, the law is that, if it is safe to do so and if another lane is available, you change lanes to avoid passing close to the police car or tow truck that is stopped on the shoulder.

 

[Evee]

I have had a similar situation. Car stopped on the shoulder but somewhat close to the line. I got the red car directly in front warning and I felt the Regen fully kick in but nothing crazy on the brakes. Then after about a second of that we passed the car and everything went back to normal.

 

[LoL Rick]

What is the appropriate response if AEB activates when it shouldn't? Will the car respond to accelerator input?

 

[javawolfpack]

What is the appropriate response if AEB activates when it shouldn't? Will the car respond to accelerator input?

Seemingly tapping the brake will disengage all AP/AEB functions and give you full manual control of the vehicle... it does it for this reason in case one of the systems is doing something wrong you can gain control.

This "feature" has led some owners to wrecking as they tapped the brake and then assumed AP/AEB would magically stop their car. In a lot of cases the AEB system re-engaged at the last minute to reduce the impact but not fully stop the vehicle. I don't have my Tesla w/ AP yet; however, if I notice an obstacle I'm just going to take back control or stop the vehicle. And let AP/AEB protect me when I have a lapse of awareness and miss something. But the tapping the brake design was brought up in a really long thread about AP wrecks on here I read.

 

[WannabeOwner]

I've had a similar thing. Car was stopped in a lay-by (slightly off the carriageway). The road did not have a hard shoulder. Car started moving as I approached and was signalling to pull out, I moved over to the outside lane (can't remember if on AP and signalled, or if no AP - but I would normally be on TACC, at least, on that road). Other car was travelling much slower than me as it rejoined the carriageway, but absolutely no danger (well, unless it decided to swerve into my lane, but on that basis any vehicle might do that at any time ...)

I got red car symbol on dashboard, noisy alerts, and all the anchors thrown out of the back ...

No other traffic on the road, but I suspect it would have been a big surprise to anything behind me.

 

[hybridbear]

During my extended test drive I had a lot of strange braking events when using TACC. I use cruise control a lot on city streets to make sure I don't accidentally speed. I did this during my overnight test drive on a parkway with lots of pedestrian & bike traffic on the paths that are about 5-15 ft off to the right of the road. The car frequently slammed on the brakes when it picked up a bike or pedestrian that was off on the paths. It mostly happened on slight curves where my road was curving & the steering wheel was turned, but the car was still reacting to the objects straight in front of it, even though the steering wheel was turned. It was super annoying. My former Fusion Energi with Ford's adaptive cruise system would have some of the same issues on that road, but not with anything near the frequency that the Model S did.

 

[GlmnAlyAirCar]

Fair enough, thanks for the clarification. It's a rather nuanced differentiation.
I'm pretty sure it AEB because TACC is never as sudden and aggressive in its deceleration. In this particular instance, the FCW and AEB kicked in very aggressively to decelerate the car as I got near the tow truck. Although I think TACC did kick in after I passed the stopped car to my right.

No, the distinction is important. TACC deceleration will happen fairly frequently. Its false-positive threshold is fairly low. It will not decelerate as abruptly as AEB (although it might be fairly abrupt). And, most significantly, the behavior you described (continued on after the threat was passed), indicates that TACC was at work.

If AEB activates, TACC is turned off. The car will not reaccelerate. Deceleration will be harsh (not "firm" like TACC, but panic slow down (not stop)). There are very few false positives. In fact, you will frequently find those posting on this forum that AEB activated improperly, and I have yet to be convinced it was AEB because in each case TACC was in use.

It's important to know which technology does what.