Authoritative summary of speed limit logic?

[brockgs]

I've been searching, but I've so far been unable to find a thread on the forum or a webpage elsewhere that definitively spells out the logic applied to how the car decides what the current speed limit should be. Does this exist, if so could someone kindly point the way?

The specific cases I face on a daily basis in my 2019 Model 3 (with full self-driving upgrade...etc)

• Car believes 40 km/h is the default speed limit in residential areas in our city when in fact it is 50 km/h. (Winnipeg, MB, Canada)
• Multiple speed limit signs not seemingly honoured even though there are no other signs around it to confuse it. There are two I pass every day that it never picks up. One indicates an increase to 80 km/h, the other changes from 80 km/h to 70 km/h. In the first case it stays at 70 km/h (the previous limit), in the second it stays at 80 km/h (the previous limit). I'm find with it not understanding conditional speed limit signs (within certain hours and/or days of week), but just a straight up sign out in the open...it *should* pickup 99.99% of the time, which it does in many other areas of the city just fine.
• Does the car fall back on any mapping data whatsoever for speed limits? Specifically, in cases where a far lane position leaves almost all speed limit signs blocked by other vehicles in lanes closer to that side of the road, I would think there would be some form of sanity check every minute or so to say "hmm, what does OSM/Google/... think the speed is here versus what I think?" It doesn't seem so which results in an annoyingly high occurrence of the car not knowing the correct speed limits.
• What is the correct way (if there is one) to flag specific errors in driving logic that are reproducible and have been on-going for months (years in my cases)?

Again, I've ready many of the threads that contain similar questions, but haven't seen (or just blindly missed, if so I'm VERY sorry) and definitive answers. There has been lots of great guesses about what the car might be thinking that leads to errors, but not if there is a known flowchart/logic-model showing the resources used and when to determine current speed limits.

Thanks in advance for anyone who's able to help point me to anything with which I can better educate myself and understand driving logic better.

Brock

 

[GtiMart]

Can you post pictures of the speed limit signs that the car does not recognize? It's possible that they are different from the training set that Tesla uses.

I believe the car "knows" a default limit on many of the roads in its map database. That map database isn't updated often on the car.

I don't have FSD so I only use autopilot on the highway. I'll let others respond to your other points.

 

[AKADAP]

At least some of the speed limit data is coming from map data. There is a road where the cars limit changes from 35 to 40 MPH where there is no speed limit sign (and the speed limit should be 40 the whole time).
Sometimes it is getting the speed from speed limit signs, and it does not always see the same sign. Driving the same road twice, the car chooses different speeds.
Sometimes I'm not sure where it is getting the speed limit from. Mt. Hamilton Rd. in San Jose CA, going up the hill, it correctly thinks the speed limit is 40 MPH, but going down hill, it incorrectly thinks the speed limit is 55 MPH. This road has so many sharp corners, and is so narrow, you are lucky to average 20 MPH.

 

[JulienW]

At least some of the speed limit data is coming from map data. There is a road where the cars limit changes from 35 to 40 MPH where there is no speed limit sign (and the speed limit should be 40 the whole time).
Sometimes it is getting the speed from speed limit signs, and it does not always see the same sign. Driving the same road twice, the car chooses different speeds.
Sometimes I'm not sure where it is getting the speed limit from. Mt. Hamilton Rd. in San Jose CA, going up the hill, it correctly thinks the speed limit is 40 MPH, but going down hill, it incorrectly thinks the speed limit is 55 MPH. This road has so many sharp corners, and is so narrow, you are lucky to average 20 MPH.

Yea, if no sign or it hasn't passed one yet (that it can identify) then it relies on the Tesla Navigation Database info which can be all over the map (is that pun???). Once it see a "standard" speed limit sign it then will set to that.

 

[brockgs]

Can you post pictures of the speed limit signs that the car does not recognize? It's possible that they are different from the training set that Tesla uses.

I believe the car "knows" a default limit on many of the roads in its map database. That map database isn't updated often on the car.

I don't have FSD so I only use autopilot on the highway. I'll let others respond to your other points.

Attached are the two specific signs I was directly referring to in my post.

Here is the first one where when I'm returning home, I'm on a road that is 80 km/h and I keep right to stay on that road at which point it turns 70 km/h. Very clear sign, no obstructions, no other signs nearby that I can possibly think would create a confusing situation. The car continues to show that it believes the speed limit is 80 km/h until another km down the road when it reaches a 60 km/h speed limit sign, which it reads and implements perfectly.:

Near the previous intersection, but going north instead of south, the road transitions from being 70 km/h to 80 km/h. 80 km/h speed limit sign is not obscured and is not near any other signs that I would think could possibly interfere with it understanding what this means. The car maintains believing it is 70 km/h until maybe another km down the road when there is yet another speed limit sign stating 80 km/h which it will *sometimes* pick up.

Apple Maps and Google Maps both know the speed limits in those areas. I will double check the OSM data later tonight. I drive on major roads that are some of the busiest in the city and well known that haven't undergone speed limit changes in as long as I can remember. But these are just two of probably 4 to 5 instances during each drive where autopilot not only doesn't pickup the clear signs, but since it has no memory, even though I have to manually roll back/forward the speed manually every day sometimes several times a day, it never learns. If the system is using underlying map data it is somehow fundamentally flawed because these roads are well established, haven't undergone fundamental changes in the past few years and have known speed limits by the two major map vendors I use.

I still love FSD / autopilot, but it does annoy me a little bit that so many years on now there *seem* to be trivial situations that it can't figure out. That said, what *seems* obvious to me may have hidden variables that I'm not aware of that are creating a situation with more complexity than FSD can handle.

Brock

 

[JulienW]

Not sure in Canada but those signs would not be standard anywhere in the US and not likely to be read as a speed limit.

 

[brockgs]

Not sure in Canada but those signs would not be standard anywhere in the US and not likely to be read as a speed limit.

I wrote it off as maybe some sort of regional thing It hadn't learned yet, but we have boatloads of Teslas despite no dealership in our province, but they are bog standard speed limit signs in our province. Every sign in the city and most in the province are exactly like this. I'd say about 90% of the signs in the city are read correctly, maybe even 95%, but that leaves an awful lot that it just doesn't see or understand that are identical in design, but something else must be interfering with it picking them up.

White sign of some standard dimension that is always the same.
The word "MAXIMUM" in black type across the top of the sign.
Two or three digits of big black type stating the speed limit.

Not sure how it could get any easier or more consistent. Speculation aside though why it is not picking them up, is there an actual way to file a specific navigation bug report to flag these signs for potential additional training?

 

[brockgs]

I wrote it off as maybe some sort of regional thing It hadn't learned yet, but we have boatloads of Teslas despite no dealership in our province, but they are bog standard speed limit signs in our province. Every sign in the city and most in the province are exactly like this. I'd say about 90% of the signs in the city are read correctly, maybe even 95%, but that leaves an awful lot that it just doesn't see or understand that are identical in design, but something else must be interfering with it picking them up.

White sign of some standard dimension that is always the same.
The word "MAXIMUM" in black type across the top of the sign.
Two or three digits of big black type stating the speed limit.

Not sure how it could get any easier or more consistent. Speculation aside though why it is not picking them up, is there an actual way to file a specific navigation bug report to flag these signs for potential additional training?

Ok, here is me taking a step back:

1. Both signs are leaning slightly
2. Both signs are separated from the road by a gravel shoulder

Perhaps the distance away from the road and the angle they are at has it questioning their relevance to that roadway...even though to a human it is clear they are standard signs, just leaning a bit and clearly could only apply to that one road they are next-ish to. Whatever the reason it seems a pretty basic use case that it is failing on. After watching the demo days videos of how it learns on all these crazy variations of signs everywhere with wildly uncommon language and materials, that this should be a slam dunk.