Unintended Acceleration - Accidentally Engaged TACC? (Roll eyes, prepare to flame me)

[Stellavator]

Never thought I would be that guy, but here I am.

let me explain exactly what happened, and let’s see if anyone can help me understand why it should have happened, or if it was indeed a system fail.

I pulled in to a pharmacy drive through, came to a stop behind a car already at the window, and the car entered Hold mode appropriately. I took my foot off the brake. When the car in front of me left, not remembering that I had left the car in drive, I put my foot on the brake, and pushed the right stalk down to engage drive. I let my foot off of the brake and placed it on the accelerator. As I pressed, the car began to move normally and as expected. This is where it got weird for a moment. As I began to accelerate, I felt the car accelerate faster than it normally would with my light peddle depression, so I let my foot off the accelerator to move it to the brake. As I did, the car continued to accelerate. Not just move, but accelerate. I got my foot on the brake, and the car responded to the brake normally. No harm, no injury. All systems work normally after I was done and drove home.

I looked and there was no overlapping floor mat on the accelerator, or any obstruction.

honestly, it felt exactly like the car does when on autopilot in traffic, when it has been stopped and begins to move again after the car in front of you starts to move, and moves fast. So I thought about my pushing of the stalk down when it was already in drive, but still in Hold mode. But you should not be able to initiate autopilot until you are moving 18 miles per hour, or something like that. You are not supposed to be able to initiate it from a stop. And to be clear, I was not in autopilot as I entered the drive through.

So, what happened? What am I missing?

And save all the fanboy defenses of Tesla at all cost. I’m plenty a Tesla fanboy myself. I just had an incident that I’m trying to understand within the context of how the car is supposed to operate. I’ve read this forum for years now, and am always skeptical of these types of reports. I paid very close attention to what was happening as soon as I noticed the car going without my input. There is no confusion about what happened, just why.

Thoughts?

 

[jjrandorin]

Any chance you double clicked the stalk down (or the car read a double click of the stalk) to put it into autopilot / noa? Only thing that comes to mind.

 

[Stellavator]

Any chance you double clicked the stalk down (or the car read a double click of the stalk) to put it into autopilot / noa? Only thing that comes to mind.

Right, I though about that. If that happened, that would represent a system failure as you are not supposed to be able to initiate it from a stop.

also, on 2020.28.6 in case anyone cares.

 

[richrootes]

Maybe the car wasn’t in full autopilot, but ‘adaptive cruise control’ mode? I’ve personally set this in traffic and have the car move off when the vehicle in front goes....

 

[Mattopotamus]

From the manual. Looks like this happened because the car in front of you was still being recognized and was more than 5 feet away.

TACC:
To use Traffic-Aware Cruise Control, you must be driving at least 18 mph (30 km/h)

If a vehicle is detected ahead of you, you can use Traffic- Aware Cruise Control at any speed, even when stationary, provided Model 3 is at least 5 feet (150 cm) behind the detected vehicle.

 

[smatthew]

Right, I though about that. If that happened, that would represent a system failure as you are not supposed to be able to initiate it from a stop.

also, on 2020.28.6 in case anyone cares.

You most certainly can initiate autopilot or TACC from a stop if there is a vehicle in front of you.

I think you engaged TACC.

 

[drtimhill]

I agree this looks like TACC engaged. However, note that the manual states:

"To use Traffic-Aware Cruise Control, you must be driving at least 18 mph (30 km/h), unless a vehicle is detected ahead of you. If a vehicle is detected ahead of you, you can use Traffic- Aware Cruise Control at any speed, even when stationary..."

So my guess is this is what happened.

 

[DirtyT3sla]

You almost definitely engaged TACC. You probably do a quick "barely press the brake as you also push the stalk down while letting off the brake" move which is the same thing I do. So since you were in hold, I assume you hit the stalk down with no foot on the brake, which turned on TACC.

If it was AP, you would have heard the chime. TACC has no chime.

 

[jjrandorin]

Also, OP, I know you were worried about flaming etc (which absolutely happens here), but your post is really laid out well, without drama and with the facts as you remember them, with enough detail for people to try to take guesses at what might have happened.

Just saying that in at least 1 persons opinion (who tends to avoid these type of threads), your post was laid out well enough to provoke thought on what might have happened, without any attempt to inspire drama.

 

[camalaio]

Almost certainly accidental cruise control engagement. I do this embarrassingly often myself, and unfortunately don't always notice immediately. Nothing bad has happened but it's enough for a "wait what's going on". Turning on cruise makes no sound, unlike engaging AutoSteer (which you can also enable from a stop). This is true for most vehicles, but for most vehicles it's not as easy to accidentally engage it by simply going into Drive.

Now, if it wasn't that, the other thing that's probable to me is an issue with Hold (the stop mode, not brake hold) if you use that. It does weird things at low speeds sometimes, including unintended acceleration (especially if one or two wheels is in a rut or something). The acceleration is still fairly gentle and it seems like you're describing something gentle as well, which is why I think this is worth a mention.

 

[Mattopotamus]

Almost certainly accidental cruise control engagement. I do this embarrassingly often myself, and unfortunately don't always notice immediately. Nothing bad has happened but it's enough for a "wait what's going on". Turning on cruise makes no sound, unlike engaging AutoSteer (which you can also enable from a stop). This is true for most vehicles, but for most vehicles it's not as easy to accidentally engage it by simply going into Drive.

Now, if it wasn't that, the other thing that's probable to me is an issue with Hold (the stop mode, not brake hold) if you use that. It does weird things at low speeds sometimes, including unintended acceleration (especially if one or two wheels is in a rut or something). The acceleration is still fairly gentle and it seems like you're describing something gentle as well, which is why I think this is worth a mention.

I feel like I do it almost every morning when leaving my garage, but because no one is in front of me, the car just beeps and me and tells me that TACC is not available.

 

[RayK]

Would it be worth it to ask Service if they can pull any logs to see what happened?

 

[pl8dlikafiddle]

Almost certainly accidental cruise control engagement. I do this embarrassingly often myself, and unfortunately don't always notice immediately. Nothing bad has happened but it's enough for a "wait what's going on". Turning on cruise makes no sound, unlike engaging AutoSteer (which you can also enable from a stop). This is true for most vehicles, but for most vehicles it's not as easy to accidentally engage it by simply going into Drive.

Just wanted to comment on the bolded part - I really believe Tesla needs to create some form of audible indication that TACC is engaged. Maybe a single ding for TACC and the typical two-tone ding for TACC + Autosteer.

 

[smatthew]

Just wanted to comment on the bolded part - I really believe Tesla needs to create some form of audible indication that TACC is engaged. Maybe a single ding for TACC and the typical two-tone ding for TACC + Autosteer.

And to tag onto that - a different tone for when TACC + Autosteer + NOA is engaged. We already get a tone when a road transitions to NOA, but it would be nice for the initial tone to indicate what mode we're in.

 

[MXLRplus]

Sidebar - Ironically, Walgreen refused to let pick up my prescription on a bicycle because "it's too risky for a bike to be in the drive-thru".

On Topic - Yes, the behavior of the TACC has changed. I have now gotten into the habit of manually shutting it off on city streets. Sometimes the brake pedal turns it off like it should, but it seems not 100% of the time on surface streets with lights present.

 

[DopeGhoti]

On Topic - Yes, the behavior of the TACC has changed. I have now gotten into the habit of manually shutting it off on city streets. Sometimes the brake pedal turns it off like it should, but it seems not 100% of the time on surface streets with lights present.

I have never seen depressing the brake pedal not disengage whichever of TACC or Autosteer happen to be enabled.

I probably am using one or the other at least 95% of the time I'm driving (or being driven by) my car, but parking lots are not a place I feel it's appropriate to have cruise control (not to be confused with Summon) of any sort engaged, because of exactly the sort of situation depicted in this thread's originating post.

 

[smatthew]

I have never seen depressing the brake pedal not disengage whichever of TACC or Autosteer happen to be enabled.

I probably am using one or the other at least 95% of the time I'm driving (or being driven by) my car, but parking lots are not a place I feel it's appropriate to have cruise control (not to be confused with Summon) of any sort engaged, because of exactly the sort of situation depicted in this thread's originating post.

Here's one for you. Ever braked at the same time as AP/TACC? Or swerved at the same moment as AP? It's freaky as heck. On multiple occasions AP has matched my maneuvers such that I staying in AP.

Oh no. Am I running on HW3? Is this all a simulation? Hello? Can anyone hear me? ;-}

 

[S4WRXTTCS]

This is clearly a UX issue.

Tesla assigned multiple functions to the same control mechanism so of course people are going to have mode confusion.

To enter the mode you wanted required you to remember which mode you were in. This is a UX failure.

There are a number of complete UX failures with the Model 3/Y.

The Gear Shift Stalk has multiple assignments
There is no on/off/interval settings for the wiper. There is only one physical control for single wipe
There is no blind spot indicator in the mirrors

On the whole Tesla does a great job at UX over the entire ownership experience (car, chargers, app, etc), but a lousy job when it consist of a driver centric UX experience.

 

[CyberGus]

Hey Elon, we need "drive-thru" mode. 'Merica

 

[Stellavator]

I agree this looks like TACC engaged. However, note that the manual states:

"To use Traffic-Aware Cruise Control, you must be driving at least 18 mph (30 km/h), unless a vehicle is detected ahead of you. If a vehicle is detected ahead of you, you can use Traffic- Aware Cruise Control at any speed, even when stationary..."

So my guess is this is what happened.

I did not know this, and that fits with what happened.