Where does it get speed limits?

[SANZC02]

• Pay attention to when you pass a speed limit sign that increases or decreases the speed limit and the length of time it takes for the dash to show the change. It can happen as you pass the sign or a quarter mile down the road, or not at all. If reading sign it would be pretty consistent.

My G1 R1S is very consistent about changing the speed limit right when I pass a standard white speed limit sign. Not construction or temporary though. It will revert to the map data speed limit down the road a ways without passing any other signs.

I’ve had the vehicle for almost 3.5 years and it has always behaved that way.

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[JacobAZ]

My G1 R1S is very consistent about changing the speed limit right when I pass a standard white speed limit sign. Not construction or temporary though. It will revert to the map data speed limit down the road a ways without passing any other signs.

I’ve had the vehicle for almost 3.5 years and it has always behaved that way.

Yes the map data is correct most of the time, so it will chang the displayed limit as you pass the sign ... but the data does exact location errors (a few hundred yards) at some locations. Here is another test, it takes a little more time. Find a speed limit sign which is changing the speed and the R1 display changes speed as you pass. Also this road has multiple lanes. Drive past the speed limit sign in the left lane with a semi or large box truck next to you on the right blocking view of the sign. The displayed speed limit in Rivian and Tesla will still change at the same point, even though the sign is not visible.

 

[SANZC02]

Yes the map data is correct most of the time, so it will chang the displayed limit as you pass the sign ... but the data does exact location errors (a few hundred yards) at some locations. Here is another test, it takes a little more time. Find a speed limit sign which is changing the speed and the R1 display changes speed as you pass. Also this road has multiple lanes. Drive past the speed limit sign in the left lane with a semi or large box truck next to you on the right blocking view of the sign. The displayed speed limit in Rivian and Tesla will still change at the same point, even though the sign is not visible.

I’ll let you go on thinking the vehicles do not read the signs, clearly you do not think they do.

Tesla and Rivian are not the only ones doing this, these days there are lots of models that blend map data and speed limit signs to determine the speed limit. A few others are Mercedes, BMW, Audi, there are others as well. Even Jeep grand Cherokees have this technology in them.

 

[JacobAZ]

I’ll let you go on thinking the vehicles do not read the signs, clearly you do not think they do.

Tesla and Rivian are not the only ones doing this, these days there are lots of models that blend map data and speed limit signs to determine the speed limit. A few others are Mercedes, BMW, Audi, there are others as well. Even Jeep grand Cherokees have this technology in them.

Don't get me wrong, I am not saying Rivian and Tesla (the only two I have have owned which display speed limit) can't detect speed signs. I am saying that real world facts show most of the time the map data is being reflected.

 

[Gen(R3)Xer]

2026 Gen 2 R1T. Where does it get the speed limits from? I assumed it read the signs but I can tell it's obviously not doing so. I routinely pass speed limit signs on several routes I normally drive and the speed limit definitely doesn't update when I pass them. On some it doesn't update within 5 minutes of passing them.

I have the same problem with my Tesla Model 3. Sometimes I’ll be on a back road and it’s displaying 25MPH while I drive by a 50MPH sign. I wonder if it’s a cellular connection issue? It has to be pulling speed limit data from somewhere.

 

[Dave Cundiff]

The trouble with using signs is that they vary in location and significance.

Some signs overhead are temporary advisory speeds. Some signs are on frontage roads, or the main interstate lanes, and can be very misleading if you're not in the part of the right of way to which the signs apply. Construction signs can look a lot like regular signs.

For more than a year, our Rivians didn't respond to CLEARLY marked speed limit signs north of Ilwaco; instead, they displayed the old speed limits that hadn't been current for seven years prior.

However, when speed limits were lowered east of Chinook, the databases were updated within a few weeks.

My best explanation of these observations: They're using a mapping database, which is updating in a more timely way each year.

Best to all!

 

[godfodder0901]

No need to take my word for it, you can easily test yourself if the speed comes from map data or camera reading. Keep in mind there is a lot off errors in the map data speeds.

• First and easiest test - Find an intersection where the roads have different speeds and there is no speed sign for a while on one when you turn from one street to the other. Drive on one turn onto the other. Usually the new speed limit will appear with no speed limit sign.
• Pay attention to when you pass a speed limit sign that increases or decreases the speed limit and the length of time it takes for the dash to show the change. It can happen as you pass the sign or a quarter mile down the road, or not at all. If reading sign it would be pretty consistent.
• This one is harder to replicate, but if you travel a route often and they recently changed the speed limit, in all probability it will take weeks or months for Rivian and Tesla to recognize the change (comes from map data)

Also, logically, the car company pays for the map data which includes speed limits. Why develop a camera system to replicate what you already paid for.

The camera tech is part of the MobileEye they purchased. You can test also by placing a homemade sign of the correct proportions in a place that has none. Then drive by. I have done this several times and it will register. Also, there is a sign on an adjacent road that my truck picks up all the time. But only in the one direction the sign is visible. I have verified this limit is not part of OSM, and Google maps displays the correct limit.

Again, it absolutely does use vision, and we can prove it.

 

[McLovin]

It's in the map data. Does not actually read speed signs.

Don't get me wrong, I am not saying Rivian and Tesla (the only two I have have owned which display speed limit) can't detect speed signs.

Those two statements seem to contradict each other. Regardless, it most definitely detects and reads the signs. Here’s how I know:

In Virginia, we have an interstate (I-66) that has HOT lanes in the middle, which are separated from the regular lanes by pylons. The speed limit in the HOT lanes is 70. The speed limit in the regular lanes changes as you head west (starts at 60, then goes up to 65).

The speed limit signs for the regular lanes is on the far right, but at the same location, the HOT lanes have speed limit signs in the space between the regular lanes and the HOT lanes (so if you’re in the left regular lane, the HOT lane speed limit sign is immediately to your left).

On occasion, when traveling in the left regular lane, the 65mph speed limit sign will be blocked from view (usually by an 18- wheeler driving in the lane to my right). The Rivian can’t see the 65mph sign, but it can see the 70mph sign for the HOT lanes to my left.

The vehicle display immediately changes to 70mph, and stays that way until I pass another 65mph sign on the right (that it can see). I’ve tested this multiple times on my commute home, intentionally keeping a large truck on my right as I pass the 65mph sign. Happens every time.

 

[JacobAZ]

The camera tech is part of the MobileEye they purchased. You can test also by placing a homemade sign of the correct proportions in a place that has none. Then drive by. I have done this several times and it will register. Also, there is a sign on an adjacent road that my truck picks up all the time. But only in the one direction the sign is visible. I have verified this limit is not part of OSM, and Google maps displays the correct limit.

Again, it absolutely does use vision, and we can prove it.

Okay last post on this thread ... trying to clear up misunderstanding.
My original post was in response to OPs question and problem with why is the displayed speed limit sometimes wrong. My answer was its the bad map data, not the camera incorrectly reading signs. Yes, I could have said that more clearly. Then there was pushback, saying its the cameras (implication making the errors the OP sees). So I provided some tests anyone can run. For example turn corner from street A to street B, with no speed sign present the display will usually change and be correct. Anyhow, the OP's original question was why is the displayed speed limit wrong sometimes. .... and your answer is?

 

[McLovin]

Anyhow, the OP's original question was why is the displayed speed limit wrong sometimes. .... and your answer is?

If I had to guess (and more to the point, if I had to design the system), I’d say:

1. Attempt to read the sign
2. If no sign, or sign unreadable, use map data
3. If map data is not available, use last known speed limit

Speed limit signs are all that matters, so it makes sense that, given the technology is available, you’d want to display the (sometimes) correct value.

Clearly saying “but, officer…the car told me the speed limit was 70.” isn’t going make a lick of difference. So in the end, it matters not what value it displays.

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