AP at a Fork, slamed brake, is this normal?

[borugee]

I was on AP, and road forked to two roads. I assume the car should have taken the main road. (Regular AP and not NoA). When car approached the fork, it started braking quickly, and I took stearing and canceled AP and took car to left. Is this expected behavior from AP? I was lucky as no one was behind me to read-end. I think this is quite not right, to slam brakes, if it see a fork in the road.

Here is a video clip to show what happened. Braking and me taking control is not very evident here, but I had to do it very quickly as AP was confused.

 

[Leafdriver333]

NoA if you have FSD, would have known what to do there but AP alone will slam on the brakes.
That's normal.

 

[Garlan Garner]

I was on AP, and road forked to two roads. I assume the car should have taken the main road. (Regular AP and not NoA). When car approached the fork, it started braking quickly, and I took stearing and canceled AP and took car to left. Is this expected behavior from AP? I was lucky as no one was behind me to read-end. I think this is quite not right, to slam brakes, if it see a fork in the road.

Here is a video clip to show what happened. Braking and me taking control is not very evident here, but I had to do it very quickly as AP was confused.

Indeed the imperfect NoA will slam on the brakes from time to time. ( A lot less than it used to ).

I don't understand what the problem is.

You should wait for Level 5 autonomy if you want a perfect autopilot to blame for not being perfect.

​

 

[1.21GW]

Your video is aligned with what I expected autopilot to do in that situation. When lanes get wide, it tries to center itself. In your case, it sends you to the middle of the fork.

 

[TomB985]

Yep, looks completely normal to me. The system is far from perfect, and is prone to confusion at forks in the road. On the upside though, it seems like autopilot behavior improves with each software revision, so we may eventually see the day where it handles the situation more appropriately.

 

[Garlan Garner]

I was on AP, and road forked to two roads. I assume the car should have taken the main road. (Regular AP and not NoA). When car approached the fork, it started braking quickly, and I took stearing and canceled AP and took car to left. Is this expected behavior from AP? I was lucky as no one was behind me to read-end. I think this is quite not right, to slam brakes, if it see a fork in the road.

Here is a video clip to show what happened. Braking and me taking control is not very evident here, but I had to do it very quickly as AP was confused.

These videos are really really hard to trust regarding AP doing this.

I don't find a problem with the driving if it was Autopilot or a Human....but ……..

 

[Electroman]

I assume the car should have taken the main road

What? I have driven that section many many times. It is a fork that splits two highways, 121 and 114. There is no way for AP to know to take left fork or right, as both of them have 65 as speed limit at that point.

Having said that it is puzzling, that why can't AP always default to the straight section, which in this case is the right fork 114). Or let the algo always follow one line when in doubt - either right or left . I prefer the left line, as this will eliminate the dive to right side exits.

 

[kramdhan]

made the same observations with AP. I am on the highway and coming up to a an off ramp merge lane on my right. When the dashed line disappears, AP moved the car slightly to the right then brought it back to the center of the lane. Seems like the car is being centered between two "known" lines

 

[ngogas]

Did you have navigate on auto pilot enabled?

 

[Msjulie]

OP's original description seems like what I have seen too often; AP tends to follow the right hand lane marking and thus will go too far right when an entrance ramp is encountered. To me, I feel the car wanted to hug-right then found that barrier up front and was all 'whoa'

 

[RayK]

This is about the same thing as what happened with the Model X last year here in the Bay Area (SB Hwy 101 at the commuter lane offramp to SB Hwy 85).

I had my first long distance experience with NoA this past weekend. It handled SB 680 from the Fairfield area all the way to the Mission Blvd exit in Fremont. Took the exit (while signaling) and returned control to me at the bottom of the ramp. Pretty nice but I'm sit going to watch traffic and the road like a hawk, with my hand on the wheel.

A couple of times it suggested that I change lanes but I was happy where I was so I cancelled it. Other times I let it move over and everything was fine.

 

[borugee]

Let me answer some of your questions.

Did you have navigate on auto pilot enabled?

Car was on AP. No NoA enable during this drive.

made the same observations with AP. I am on the highway and coming up to a an off ramp merge lane on my right. When the dashed line disappears, AP moved the car slightly to the right then brought it back to the center of the lane. Seems like the car is being centered between two "known" lines

This is not an highway, but road divides to 2 I was driving on AP enabled. When it saw the road divides into 2, car did not know which way to take and started applying brakes. This may be normal behavior of AP system, but can be a safety issue, if it stops in the middle of the road with brakes.

 

[borugee]

What? I have driven that section many many times. It is a fork that splits two highways, 121 and 114. There is no way for AP to know to take left fork or right, as both of them have 65 as speed limit at that point.

Having said that it is puzzling, that why can't AP always default to the straight section, which in this case is the right fork 114). Or let the algo always follow one line when in doubt - either right or left . I prefer the left line, as this will eliminate the dive to right side exits.

That is the point I am making also, it has to either take left or right. Middle of the road braking is no good. That is what happened to me, I had to take over quickly to go left in this case.

If this is how AP is programmed to behaves, good to know. Also as some others pointed out, AP is still work in progress, and never to be trusted, need to baby sit all the time.

 

[Tam]

...This may be normal behavior of AP system, but can be a safety issue, if it stops in the middle of the road with brakes.

I guess you haven't got "phantom brake"--brake that you look around and can't figure out any good reasons for it.

You are lucky that you've got a brake with a reason: a fork.

You are even luckier because it didn't go straight into a gore point as @RayK mentioned as in the fatal Autopilot to the Apple engineer.

But you are right that it should pick 1 way or other and not brake and not slamming into a gore point.

Autopilot will eventually get better but it might take a long time.

In the mean time, the instant solution is to use Navigation on Autopilot as mentioned by @Leafdriver333 .

 

[TMThree]

What? I have driven that section many many times. It is a fork that splits two highways, 121 and 114. There is no way for AP to know to take left fork or right, as both of them have 65 as speed limit at that point.

Having said that it is puzzling, that why can't AP always default to the straight section, which in this case is the right fork 114). Or let the algo always follow one line when in doubt - either right or left . I prefer the left line, as this will eliminate the dive to right side exits.

It doesn't have to be one or the other. AP knows if you are in the far left or far right lane of a multiple lane road. That means it can follow the left line when on the right lane, or follow the right line when in the left. No need to center exactly in the lane either, just keep a reasonable distance from the line (you can use the average distance used for the previous X minutes you had been driving on this road as reference) instead of trying to immediately swing to the center.

 

[SMAlset]

This is about the same thing as what happened with the Model X last year here in the Bay Area (SB Hwy 101 at the commuter lane offramp to SB Hwy 85).....

From what I remember of the details that the investigation had released, this was not like the Mt. View accident. That one the car was following a vehicle in front of him who decided to quickly switch lanes to the right. Unfortunately for the Tesla driver where that happened it was in a poorly marked area and the car didn’t gave good lines to follow. I don’t think saying this driving encounter is like that one at all is fair. And besides when the car encounters two very distinct paths to travel—ie two highways like this that split —as a passenger I wouldn’t know which one the driver was planning to take either! Unless the car had a destination programmed in don’t know how the car is suppose to know which direction to take in this case. Even the lane markings there indicate a straight or a path to the right in the lane the was driving in before reaching this highway split.

 

[Triplett]

I knew it was a bad idea to hire Robert Frost as the Director of Autopilot...

 

[Jim R]

Maybe I'm off base here, but since a human was responsible for the car, the human should have chosen which way to go. Why leave this to the car? There were two choices, and you didn't tell the car where you were going, what your destination was. Speaking as a human, I'd wonder which way to go myself - but I would know my destination and choose accordingly. I agree with others that braking might not be the best solution. Defaulting to the right might be better.

 

[Electroman]

This is not an highway, but road divides to 2 I was driving on AP enabled. When it saw the road divides into 2, car did not know which way to take and started applying brakes. This may be normal behavior of AP system, but can be a safety issue, if it stops in the middle of the road with brakes.

I don't know if i should take you seriously or you are trolling here. That section 65 mph IS A highway, where 121 and 114 splits (see google map below). Next from your video, it didn't look like it was slamming the brakes. It slowed down and if you had not taken over, it would take the right or the left highway but would have been very jerky. How do I know? I have gone through this section over 100 times in the last many years, both on AP1 and 2.

Also as some others pointed out, AP is still work in progress, and never to be trusted, need to baby sit all the time.

Never to be trusted? Yes for someone who does not have basic common sense. You can 100% trust AP when there is no decision to be made. When there is a decision to be made, or when the lines are faded it needs your assistance. Thats all. I normally switch to a different lane before I reach that point, so that AP does not have a need to make a decision. You absolutely don't need to baby sit all the time, but you just need to chaperone.

These kind of statements, "cannot be trusted", "will kill you", "need to baby sit all the time" is insulting to many of us who use it for everyday commute, including that very same stretch that you are alluding to.

 

[afadeev]

I was on AP, and road forked to two roads. I assume the car should have taken the main road. (Regular AP and not NoA).

The car really doesn't know what the "main" road is, or should be.
And yes, Y-intersections are the kryptonite for Tesla's AP. At all speeds, and under all circumstances.

Two ways for you to potentially mitigate your situation:
1). Drive under Navigate on AP, which would manifest a preference to bear left or right at that intersection.
2). Drive in the right-most lane, to remove the turn decision from AP's consideration.
3). Drive behind another car, if available. AP will follow and do whatever the leading car is doing.

When car approached the fork, it started braking quickly, and I took stearing and canceled AP and took car to left. Is this expected behavior from AP?

I would not call it "expected", as that is certainly not what I would expect AP to do.
But it is the typically "observed" AP behavior, sadly.

I was lucky as no one was behind me to read-end. I think this is quite not right, to slam brakes, if it see a fork in the road.

I've learned to pro-actively cancel AP at Y-forks, as the car will randomly either pick one of the 2 roads to follow, brake suddenly and swerve around, or head straight down the middle of the two roads.
It is what it is.

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