Phantom Speed Reductions

[Kevy Baby]

Okay, I know this topic has to have been covered, but I am unable to locate. Point me in the right direction if it has been.

I know phantom braking has been discussed ad nauseam, but what about phantom speed reductions? On my daily commute I have three specific locations where TACC max speed reduces from my preset value (65 MPH or higher) to 55 MPH

• It is always in the exact same spots every time - all three spots are at the end of a transition merge of car pool lanes
• It did it when I had just AP and continues to do it with EAP which I added last week
• Oddly, the position of each moved back by ~100 yards with a SW update a couple of iterations ago (the one before 2020.36.x)
• None of the freeways I drive have speed limits less than 65 MPH
• It's annoying AF

So - anyone else experience this?

 

[john5520]

Search Phantom Braking and you'll see complaints about this. Bad mapping data is named as the culprit and the 40.3 should help remedy this on the freeway if the speed sign reading feature works as advertised. This update is currently being distributed, but I haven't gotten it yet. Part of my commute to work is on a 55 mph freeway marked as 45 mph for most of the way. It's common and has been issue for a long time from what I gather. Yet another problem I'd like to hear someone from Tesla discuss in detail. Specifically, why does it taking so long for the mapping data to be corrected.

 

[Kevy Baby]

Search Phantom Braking and you'll see complaints about this.

But this is different (at least from all the things I've read). How I am trying to discern:

• Phantom Braking is where the car just suddenly brakes, but it is typically momentary and you can accelerate back up
• Phantom Speed Reduction is where the max speed setting of TACC (as displayed on the screen) is suddenly reduced (and the car starts to slow)

I see a lot of discussion about the first detail but not the second. What strikes me as odd is that the three consistent places I experience it is where two carpool lanes (from two separate freeways) come together. And one of them is about a mile past the non-carpool merge is (for those in Orange County, CA it is the 55 North merging onto the 5 North).

I have only driven past one of the transitions NOT in the carpool lane one time - the same speed reset occurred in the same place. But this is not a significant data point.

 

[KenC]

I have the bad mapping issue. On my 40mph two lane country road, someone stuck up a 15mph sign. Of course, the robo-mappers must have picked up the sign, and now that spot on the road is 15mph, and forces the Model 3 to slow down! Of course, it's not correct, since there's no matching sign on the other side of the road, and the only locations with a 15mph sign are schools and fire departments, and those are 25mph, except when there's a flashing light. How the robomappers could assume the 15mph limit was correct, is ridiculous.

Does anyone know the mapping database the Tesla uses and to whom we'd send corrections?

 

[DopeGhoti]

Just paint the "1" into a "4" and you're back in business next time the car's camera sees the sign!

 

[john5520]

But this is different (at least from all the things I've read). How I am trying to discern:

• Phantom Braking is where the car just suddenly brakes, but it is typically momentary and you can accelerate back up
• Phantom Speed Reduction is where the max speed setting of TACC (as displayed on the screen) is suddenly reduced (and the car starts to slow)

I see a lot of discussion about the first detail but not the second. What strikes me as odd is that the three consistent places I experience it is where two carpool lanes (from two separate freeways) come together. And one of them is about a mile past the non-carpool merge is (for those in Orange County, CA it is the 55 North merging onto the 5 North).

I have only driven past one of the transitions NOT in the carpool lane one time - the same speed reset occurred in the same place. But this is not a significant data point.

There's been a lot of talk about it. For some (including myself), the slowdown between these 'phantom' speed transitions was very abrupt rather than gradual, so it got lumped in to many phantom braking threads. I myself have mentioned it several times in the bigger threads.This is a well known problem that we don't have all the answers for besides knowing it's caused by bad data.

 

[Eddie123]

I've had similar phantom braking issues, but mainly along 5 North, right lane, near the Newport Blvd overpass. The issue is intermittent, but I believe it's related to the front camera, as it can see the traffic lights at the traffic below the overpass at certain angles. I'm still very careful driving in that area.

On city streets, I discovered one reason why it phantom braked on one of my commonly travelled streets. For months, I couldn't understand why the car braked from 40mph to 20mph along Tustin Blvd at the same spot every day. Then, one day I saw a partially skewed stop sign on a small side road. The camera was sensitive enough to pick up the small partially blocked stop sign as if it was located on the street I was driving. Mystery solved.

I turn on full autopilot nearly 90% of my time, from the city streets to the freeways. I had the car for 6 months now, and I have enough full confidence of its capability on the freeways. I let the car decide when to switch lanes without approvals. I do have to intervene at least once a day mainly on merging to the rightmost lane near an onramp.

 

[Kevy Baby]

There's been a lot of talk about it. For some (including myself), the slowdown between these 'phantom' speed transitions was very abrupt rather than gradual, so it got lumped in to many phantom braking threads. I myself have mentioned it several times in the bigger threads. This is a well known problem that we don't have all the answers for besides knowing it's caused by bad data.

Thanks John. As I suspected, it WAS covered in the Phantom Braking threads (even though, IMO, it is a different problem than phantom braking). I guess I gave up too soon on those threads. I shall learn to live with it.

 

[SlimJim]

I have phantom slow down section on my commute. It didnt slow down the last two days mysteriously.
It kept cruising on at 70 mph. 60 zone. Used to slow to 58. I was like atta boy!

 

[COS Blue]

Reviving an old thread here but -- why does the TACC reduce its speed at all? I was driving on I-25 through Denver the other day with TACC set to 60mph or whatever... car started slowing down and I looked and my TACC had reset itself to 30mph! This was without Autosteer. I thought it would only reduce my speed for me if I had Autosteer turned on (because it only allows up to 5mph over the speed limit).

This has happened on C-470 a few times too (another limited-access highway). I don't drive in Denver a whole bunch so I'm always surprised when this happens.

 

[clydeiii]

You just need to fix Tesla's maps data.

 

[Fernand]

I forget where it is, but people HAVE edited some maps. It was discovered in connection with incorrect parking lot maps.

I have a daily spot where Nicki ignores an advisory 30 MPH sign and tries to barrel down a narrow merge "tunnel" at 65 MPH (from highway 24 Eastbound to highway 13 southbound), then apparently notices some 35 MPH sign on the side and resets the target speed to 35 MPH on freeway 13 southbound just AFTER merging with traffic. Aaaagh! Novices would complain about Phantom Something It's an exercise in scroll wheeling. I've reported it to the FSD Beta team with no results for many many months.

 

[Kevy Baby]

Reviving an old thread here but -- why does the TACC reduce its speed at all?

Well, because it still needs work. FWIW, it is a lot better than it used to be in just my 2.5 years of ownership and where I started is apparently much better than before.

I have a couple of sections of my daily commute where the speed suddenly drops at the EXACT same places. They happen to be going over or going under a surface street so perhaps a map misinterpretation is taking place. I also see my TACC preset speed drop down to the speed limit (or lower) after going through a freeway transition (whether I was transitioning or just passing through. I can predict the spots within 50 feet every time.

Annoying? Yep. Some day this won't happen. In the mean time, I just roll with it.

(And I have a spot on my drive home where the automatic wipers kick on, even when there isn't a cloud in the sky in the middle of the day.)

 

[TresLA]

Thanks John. As I suspected, it WAS covered in the Phantom Braking threads (even though, IMO, it is a different problem than phantom braking). I guess I gave up too soon on those threads. I shall learn to live with it.

Yes, people often call it phantom braking when it’s not.

 

[Kevy Baby]

Yes, people often call it phantom braking when it’s not.

And it is always a lethal safety hazard when it happens (people have engaged in this level of hyperbole here)

 

[dawnerd]

I'm on latest FSD Beta and it still reads the 55mph truck signs as normal speed limits and slows down. Not all the time - usually when there's two in a row. What's weirder is I'm in California and you'd think they'd have the freeways here pretty well worked out. Even more frustrating is sometimes it'll pick up the signs and not change the speed, other-times it decides going 70+ is too fast and will bump down to 55.

There's a stretch of I5 going to/from Disney that's really bad but that's mostly map data. The car thinks you've jumped onto a side road and bumps down to 35. Super frustrating.

 

[COS Blue]

I read on a different thread (sorry don't remember which one) that if you set the speed to your current speed (like up or down on the stalk for MS) then it won't automatically reduce your speed based on the (correct or incorrect) speed limit. If you set to speed limit offset (which I guess is what happens when you pull the stalk toward you on MS), then it stays pegged to the speed limit (which it sometimes is wrong about). Haven't yet tried this to verify that it works.

 

[Kevy Baby]

I read on a different thread (sorry don't remember which one) that if you set the speed to your current speed (like up or down on the stalk for MS) then it won't automatically reduce your speed based on the (correct or incorrect) speed limit. If you set to speed limit offset (which I guess is what happens when you pull the stalk toward you on MS), then it stays pegged to the speed limit (which it sometimes is wrong about). Haven't yet tried this to verify that it works.

To the best of my recollection, I have not had my speed change due to reading a sign, except on surface streets, where TACC will always limit your speed to 5 MPH over the posted limit. And even then, it is not based on street signage as much as it changes due to the map database (it know the speed limit lowers at a certain point and automatically reduces the speed - even if it hasn't read a sign yet.

On the highway, I have seen the far right speed (not sure what that is called) adjust based on speed limit signs, including dropping to (for example) the lower TRUCK speed limit, even immediately after reading the regular speed limit sign. However, this does not impact the TACC set speed of the vehicle.

MAJOR CAVEAT: @dawnerd is on B_FSD, so that may act differently

 

[dawnerd]

To the best of my recollection, I have not had my speed change due to reading a sign, except on surface streets, where TACC will always limit your speed to 5 MPH over the posted limit. And even then, it is not based on street signage as much as it changes due to the map database (it know the speed limit lowers at a certain point and automatically reduces the speed - even if it hasn't read a sign yet.

On the highway, I have seen the far right speed (not sure what that is called) adjust based on speed limit signs, including dropping to (for example) the lower TRUCK speed limit, even immediately after reading the regular speed limit sign. However, this does not impact the TACC set speed of the vehicle.

MAJOR CAVEAT: @dawnerd is on B_FSD, so that may act differently

Did some more testing and it appears it's the R6-4(CA) sign in particular that trips up TACC. See page 43 https://dot.ca.gov/-/media/dot-medi...rnia-manual-for-setting-speed-limits-a11y.pdf