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Reading speed limit signs

tonybelding

Active Member
Aug 17, 2006
1,484
835
Hamilton, Texas
Years ago when I had my Roadster in the shop for service, I got a Model S loaner with the old Mobileye system. It had its shortcomings, but one thing that did impress me was its reading of speed signs — not quite flawless, but pretty darn close. Autopilot was also able to adjust its speed automatically whenever entering and exiting speed zones, which was highly convenient.

When I bought my new Model S this year, I was disappointed that Autopilot no longer adjust its speed automatically, aside from reducing to the speed limit (whatever the car believes that to be) plus 5 MPH. So, I was back to watching carefully for speed changes and nudging the stalk as needed. I also gradually realized that the car was no longer reading speed signs at all, but instead was relying on Google’s map data, which is occasionally wrong.

I read an article asserting that Teslas no longer read speed signs because of a Mobileye patent, but they were developing a work-around. With the latest software update in my Model S, the work-around has arrived! And the result…

It’s not good. It seems to read signs OK in town, but I haven’t yet seen it correctly read a sign higher than 60 MPH. This is particularly annoying when leaving town on the highway and going from the 60 zone to 75, because then autosteer is restricted to 10 MPH below the actual posted speed limit. The only fix is to pull off on a side road, then immediately back to the highway, at which point it “forgets” all about signs and reverts to the Google map data.

In addition to being blind to 70 and 75 MPH signs, it also was very confused by the highway construction, work zone 65 MPH signs. It saw them, but it read the first one as 45 MPH and the second as 55 MPH. Pulling off the road and back on caused it to revert to Google’s also-incorrect 75 MPH.
 
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SSonnentag

埃隆•馬斯克
Apr 11, 2017
1,768
2,380
Arizona
I'm seeing pretty much the same thing in my S. It almost never reads a sign correctly and, like you said, suffers from CRS (can't remember speed :p) when re-entering a roadway that it had previously seen the sign for.
 
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arghx7

Member
Aug 6, 2019
523
606
Michigan
I've only tested it around town, but so far it works well. There's a road through a shopping center with a 25mph sign that it now reads correctly, instead of using the 45mph from GPS.
 
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byeLT4

Member
Feb 16, 2017
791
917
Texas
Mine had been working well with the previous update, at least on my route home. The increments from 55,60 and then 75 would happen immediately after I passed the sign (I'd still have to manually adjust it, but it was correct on the display at least). The latest update seems to have caused it to revert back to the old ways. Hasn't picked up the 75 MPH sign since and the others it now appears to be based off of a specific location rather than the sign.
 

Az_Rael

Supporting Member
Supporting Member
Jan 26, 2016
5,667
8,962
Palmdale, CA
Just got the update in my 3 last week. Two drives to work have seen a decidedly mixed ability to catch speed limit signs. It unfortunately has made performance worse because when it misses a sign long enough, it seems to default to 45 mph vs the old 65mph map data, so I will randomly have AP slow way down, where before it just didn't work, so at least it was consistent.


Hopefully it improves over time. Would be nice to catch up to our AP1 S on this 20 mile section of my commute.
 

Nikki's Dad

Member
Jan 11, 2016
85
65
Atlanta, GA
So far, my car has read speed limit signs correctly most of the time. A notable miss was its consistant inability, on a long drive I recently took, to see 65 mph signs when leaving a 55 mph zone (resulting in being stuck at 60 mph without manual override). Another interesting thing I experienced - I purposefully positioned my car so that a truck would obscure a speed limit sign indicating drop in the speed limit to 45 mph (down from 55 mph) to see if the car would default to using the GPS data as a back up. It did not, at least for the short time I was in the 45 mph zone.
 

SSonnentag

埃隆•馬斯克
Apr 11, 2017
1,768
2,380
Arizona
I can't say I noticed... I thought with at least TACC it adjusts? Otherwise it's just a visualization/display.

It would be only for visuals without AP or TACC enabled (if signs are read on TACC), except for when you go to engage AP or TACC it doesn't know the correct speed limit as it hasn't been reading the signs. I'm sure it will improve over time though.
 

J1mbo

Active Member
Aug 20, 2013
1,609
1,459
UK
It’s not good. It seems to read signs OK in town, but I haven’t yet seen it correctly read a sign higher than 60 MPH. This is particularly annoying when leaving town on the highway and going from the 60 zone to 75, because then autosteer is restricted to 10 MPH below the actual posted speed limit. The only fix is to pull off on a side road, then immediately back to the highway, at which point it “forgets” all about signs and reverts to the Google map data.

From the release notes:

Speed Assist now leverages your car’s cameras to detect speed limit signs to improve the accuracy of speed limit data on local roads.

So far, I have found it has the same shortcomings of the Mobileye system: it reads the limits from adjacent roads and ignores repeaters that are painted on the road. I haven't driven behind a truck with a "speed limited" sticker on the back yet... that always used to fool the Mobileye system.
 

Daniellane

The Tesla Guy
Supporting Member
Aug 13, 2017
2,623
3,463
Camas, Washington
I did some testing early on. No TACC or AP engaged.
I’ll have to test higher speeds on the freeway.
Quick 2 minute video
Tesla 2020.36 Speed Limit Sign Recognition & Green Light Chime
 
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