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Auto pilot not adjusting to speed limit?

I have autopilot on my MY set to drive 4 mph over the speed limit. It usually works fine, but recently on the highway the speed limit dropped from 70 to 60 and the car kept going at 74 MPH. The screen displayed the 60 mph speed limit sign, and when I double tapped it the speed adjusted down to 64, so I know the car was aware of the speed limit change. Any idea what's going on?
 

Gor-Gor

Member
May 23, 2021
209
280
Oklahoma
I have autopilot on my MY set to drive 4 mph over the speed limit. It usually works fine, but recently on the highway the speed limit dropped from 70 to 60 and the car kept going at 74 MPH. The screen displayed the 60 mph speed limit sign, and when I double tapped it the speed adjusted down to 64, so I know the car was aware of the speed limit change. Any idea what's going on?
Do you have it set to current speed, or speed limit?
 
Do you have it set to current speed, or speed limit?
It’s set to Speed Limiy +4 mph fixed offset.

like I said, most of the time it works exactly as expected - if I’m in a 55 zone that drops down to 45 then goes back up to 55 the car drives at 59, slows down to 49 and then speeds back up to 59. It just fails to do so once in a while despite having ‘seen’ the speed limit sign.
 

Fourdoor

Active Member
May 31, 2016
1,220
1,140
United States
It’s set to Speed Limiy +4 mph fixed offset.

like I said, most of the time it works exactly as expected - if I’m in a 55 zone that drops down to 45 then goes back up to 55 the car drives at 59, slows down to 49 and then speeds back up to 59. It just fails to do so once in a while despite having ‘seen’ the speed limit sign.
For me, sometimes it works, sometimes it doesn't. I also notice that it doesn't see speed limit signs until you are passing them, so in speed trap areas even if it works perfectly, you have to manually lower speed to avoid a potential ticket.

Keith
 

frankvb

Member
Supporting Member
Feb 29, 2020
941
586
San Diego, CA
Assuming that auto steering was enabled - your speed (above the speed limit) will not be limited on freeways - manually you can override to e.g. 80 mph with a 65 mph speed limit even when on auto steering. On city streets it will limit that to 5 mph over the limit.

With only TACC activated it won't change your set speed at all.
 
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Fourdoor

Active Member
May 31, 2016
1,220
1,140
United States
If you are already above your offset when you activate autopilot, it will stay there and not adjust as the posted limit changes.

This is true on the highway, but on non-highway roads where you are limited to 5 mph over the limit, it will adjust down as needed to maintain no more than 5 mph over the limit and (most of the time) then adjust back up when the speed limit goes back up... but not always. The "not always" is the annoying part. I would rather it NEVER did it than having it do it sometimes but not other times at random.

Keith
 

frankvb

Member
Supporting Member
Feb 29, 2020
941
586
San Diego, CA
Bingo. Now the question is WHY? I just got back from a 2K road trip and was annoyed with TACC ignoring “posted” speed limit changes. Seems like an easy fix and since this could be considered a major SAFETY feature one would think the car could do this.
Be careful what you wish for - close to me there is a freeway bridge under construction, and there's now a (significant) lane shift that causes AP to think you are not on the freeway but on a road with a 40 mph speed limit. I now manually kick it out of AP before going there, as it will slow down a lot (I wouldn't call it slamming on the brakes but it is rather unnerving).

Second thing is that the speed limit as displayed/detected by the car is frequently wrong (too low or too high) so you can't really rely on it. I blame Tesla's map provider in combination with their implementation of the speed sign reading. My previous BMW was very accurate so it's definitely possible to improve this a lot. As an example, turning into my neighbourhood (onto a clearly residential road/area) the speed limit stays at 50 for a while.
 

TomServo

Active Member
Apr 10, 2014
1,750
1,174
Belleville IL
Be careful what you wish for - close to me there is a freeway bridge under construction, and there's now a (significant) lane shift that causes AP to think you are not on the freeway but on a road with a 40 mph speed limit. I now manually kick it out of AP before going there, as it will slow down a lot (I wouldn't call it slamming on the brakes but it is rather unnerving).

Second thing is that the speed limit as displayed/detected by the car is frequently wrong (too low or too high) so you can't really rely on it. I blame Tesla's map provider in combination with their implementation of the speed sign reading. My previous BMW was very accurate so it's definitely possible to improve this a lot. As an example, turning into my neighbourhood (onto a clearly residential road/area) the speed limit stays at 50 for a while.

I thought when the car read a speed sign it over rode the hard coded nav data? That’s not true?
 

Fourdoor

Active Member
May 31, 2016
1,220
1,140
United States
Second thing is that the speed limit as displayed/detected by the car is frequently wrong (too low or too high) so you can't really rely on it. I blame Tesla's map provider in combination with their implementation of the speed sign reading.

This one is really annoying. One section of my daily commute was a construction zone about 2 years ago. My MYP slows down for the 45 mph construction zone speed limit every day on my commute... but only on the "towards work" leg of the round trip, on the way home it doesn't slow down for this "ghost construction zone" that hasn't existed for 2 years. I have started doing a "bug report" for the ghost construction zone in hopes of getting them to update their maps. It also thinks the unmarked road for the last 2 miles of my commute is 20 mph as if it is a residential zone when it is actually 45 or 55 (not sure due to lack of signs...I need to find out for sure)... I just drop out of AP for that section. After I investigate and find out the "real" speed limit in that section I will start doing bug reports for it as well.

Keith
 

animorph

Active Member
Apr 1, 2016
2,164
1,586
Scottsdale, AZ
If you are on a road where the Autosteer speed limit + 5 MPH limit applies the car will adjust it's speed up and down to stay at that +5 limit. The main gotcha is that you have to have had the max limit set to something high enough that AP had to slow down to get to the +5 limit. Then it will slow down as needed. It will speed up as allowed, UNTIL it reaches your previous manually set max speed. It will not exceed that setting.

So if you start with a manually set 60 MPH and hit a patch through town that is 45 MPH and Autosteer is subject to the +5 limit, the car will automatically slow to 50 MPH. If the speed limit increases to 50 MPH the car will speed up to 55 MPH. If the speed limit increases to 70 MPH the car will set the max speed back to 60 MPH, but will not automatically go beyond that. The same will happen if Autosteer decides the +5 limit is no longer applicable, the max speed returns to 60 MPH.

That leaves you in control of the car. It would be nice to have the car automatically adjust the max speed. One of my tougher jobs while driving in AP is to watch for speed limit signs. I assume that will be one benefit of FSD.
 
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frankvb

Member
Supporting Member
Feb 29, 2020
941
586
San Diego, CA
I thought when the car read a speed sign it over rode the hard coded nav data? That’s not true?
I haven't been able to deduct much logic in how this works, you would think that is the logical approach but it doesn't seem to work like that.

As an example, going past an intersection the speed limit changes from 45 to 40. There's a 40 sign only on the right side (3 lanes) which is very difficult to read and easily blocked from view. If the car 'sees' it, it picks up the speed limit change, however if it misses it, it stays at 45. Obviously in this case the map data should have 40 for that stretch of road.

It actually seemed to have worked better (at least in this case) before the 'read speed sign' functionality was implemented.
 

melsee

2019 M3LR
Sep 8, 2020
6
5
Houston, TX
I haven't been able to deduct much logic in how this works, you would think that is the logical approach but it doesn't seem to work like that.

As an example, going past an intersection the speed limit changes from 45 to 40. There's a 40 sign only on the right side (3 lanes) which is very difficult to read and easily blocked from view. If the car 'sees' it, it picks up the speed limit change, however if it misses it, it stays at 45. Obviously in this case the map data should have 40 for that stretch of road.

It actually seemed to have worked better (at least in this case) before the 'read speed sign' functionality was implemented.
Is there a setting to drive the posted speed limit - going through small towns I like to dive the posted speed but it seems to want to drive the posted speed plus 5 miles
 
For me, sometimes it works, sometimes it doesn't. I also notice that it doesn't see speed limit signs until you are passing them, so in speed trap areas even if it works perfectly, you have to manually lower speed to avoid a potential ticket.

Keith
It is super annoying that the car does not slow down until it passes the lower speed limit sign. A prudent human would start slowing down as soon as they see the sign, so that the vehicle speed is right when passing the sign. I have been on many highways that pass through small towns and the speed limit suddenly drops by 20, 30 or even 40 mph. If you are not vigilant to watch for these signs, cops will ask you to contribute to the revenue of these small towns. This type of speed adjustment is exactly one of the things I would expect FSD to do for me to reduce the stress of driving on a road trip.
 
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Madsen203

May 26, MYLR, White ext, Black int, Tow, 19”
Jun 1, 2021
554
411
Bay Area
11.103 seems to work fine for me. I will avoid updates until they release it for the “standard update” as opposed to advanced update. It has improved in the 2k I’ve put on the car and now is fairly stable. I’ve had only one phantom brake in the few hundred miles of use. The stop and go traffic use still sucks and isn’t smooth enough for me but casual highway and light traffic above 30mph it is rock solid.
 

edub

Member
Jan 4, 2020
7
4
Iowa
It is super annoying that the car does not slow down until it passes the lower speed limit sign. A prudent human would start slowing down as soon as they see the sign, so that the vehicle speed is right when passing the sign. I have been on many highways that pass through small towns and the speed limit suddenly drops by 20, 30 or even 40 mph. If you are not vigilant to watch for these signs, cops will ask you to contribute to the revenue of these small towns. This type of speed adjustment is exactly one of the things I would expect FSD to do for me to reduce the stress of driving on a road trip.
I’m in the same situation. Speeds will drop from 55 to 35 when I get to smaller towns, which is a common occurrence here in Iowa. It doesn’t begin to slow down until I get to the 35 sign. I tried manually reducing it down to 35 a couple times, but it took too long for it to slow down. I now end up having to disengage and brake on my own. Currently running 2021.36.5.3. Hoping it changes for the better with a future version because it does get a little annoying.
 
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