detected speed limit very wrong

[RSouthern]

Anyone see this problem before and what would it mean if you had active cruise control set to follow the limit? BTW, the speed limit in this neighborhood is 15 mph, and the area before it was 35. The Porsche continued to show 65mph as the limit past multiple signs posting speeds of 35, 40 and 15. Normally it detects correctly. Glad I didn't have the cruise set today!

Sponsored

 

[W1NGE]

Yep it's pretty hit or miss and relies on various input not just what the camera sees as I understand it.

I disabled anything on my Taycans which were dependent on "knowing" the speed limit due to the random (aka dangerous) braking due to misreading.

I think the mapping data is part of the issue.

My 992.2 has the same issue at the same spots as my Taycans did so it's not limited to the Taycan.

 

[MrJones02]

It works ok most of the time, but certainly not all the time. If a computer can't detect all of them without fault, they do expect a driver to pick up on each and every one of them, while also keeping an eye on traffic, cyclists, pedestrians ...
I always have Waze open, it also shows the speed-limit and found that one to be very accurate, when in doubt I follow whatever Waze shows me.

 

[4sCT21]

Yep, the residential road near me is apparently 50 mph lol

This is why they can not allow the cars to dictate the speed you drive at.

My wife's old Mazda told me to do 20mph on the motorway ....

 

[Tighlines]

Sorry, have to ask...
You set the cruise control on residential streets? Or is this a hypothetical scenario?
Mine is wrong sometimes too but it doesn't bother me cuz I turn off all driving assistant modes. If I wanted the car to drive me I would've bought a tesla.

 

[4sCT21]

Sorry, have to ask...
You set the cruise control on residential streets? Or is this a hypothetical scenario?
Mine is wrong sometimes too but it doesn't bother me cuz I turn off all driving assistant modes. If I wanted the car to drive me I would've bought a tesla.

EU legislation / directives (i believe) are moving toward cars detecting speed limits, and not allowing the driver to exceed that limit, hence my comments.

Cars can not be relied upon to recognise speed limits. They pick up speed limits of adjacent side roads, off the back of lorries etc its dangerous.

Definitely cant use cruise control in residential areas, too busy dodging potholes ?

 

[kempez]

Cars can not be relied upon to recognise speed limits. They pick up speed limits of adjacent side roads, off the back of lorries etc its dangerous.

Definitely cant use cruise control in residential areas, too busy dodging potholes ?

Agreed with this. None of the cars I've ever driven with this functionality can consistently get all of the speed limits right, especially on our random and occasionally ill-marked UK roads!

 

[RSouthern]

Let me be clear, I don't usually use ACC/Innodrive with the limit on most ground streets, but the road that goes to this neighborhood (where I took the picture) is a country road that's a 35mph limit and about 6 miles long and relatively straight, so I do tend to use the system through here from time to time. Where the limit drops to 15mph is in a tight/narrow area and no, I wouldn't dream of using cruise or self drive there. But 65 in a 35 is still way too fast. Of course most people would catch it but there are not that many signs so someone new to the area may not know the local limit.

What's concerning to me is that the system appeared to get stuck. It showed 65mph as the limit through multiple speed limit change areas (50, 40, 35 and finally 15), like that function was hung. the only place anywhere around that is 65 are the main freeways (85 and 87 for those in South San Jose) and that was 10-15 miles prior to taking that picture. What would happen if the speed limit detection got stuck in a construction zone (lower limit), or where a congestion limit was active (like in the UK) and the car was stuck on a higher limit. You might miss the sign and the car wouldn't adjust it's set speed down until the driver reacted/realized there was a problem. I also wonder about how it would handle resume.

And just to address some of the messages, the system usually displays the correct limit. For example, driving out of the same neighborhood this morning it showed 15mph, the correct limit. It was stuck last night, displaying a speed from much earlier in the drive.

 

[RSouthern]

EU legislation / directives (i believe) are moving toward cars detecting speed limits, and not allowing the driver to exceed that limit, hence my comments.

Cars can not be relied upon to recognise speed limits. They pick up speed limits of adjacent side roads, off the back of lorries etc its dangerous.

Definitely cant use cruise control in residential areas, too busy dodging potholes ?

I think some modern cars are starting to use computer vision systems to read road signs (my wife's 2020 BMW X7 appears to do this), backed up by map data from the nav (think Waze, Google maps etc). It makes sense to have that information available to driver since there are a lot of roads in the US that don't have regularly posted or clear speed limit signs. What the car does with that data is an entirely different question which the EU appears to be trying to regulate to standardize it.

But my point I was trying to make with the original and follow-up posts is, the system that does the speed limit detection, in at least my '22 Taycan, got stuck and stopped updating the limit. I am concerned that if that system is interacting with the ACC/Innodrive system to modify the set point in the cruise control, that *could* lead to some unexpected behaviors. Yes, the driver should always be monitoring and yes, you should be smart about when and where you use ACC/Innodrive, but in the real world there are a lot of things happening and this appears to be adding one more thing to the task list.

 

[4sCT21]

I think some modern cars are starting to use computer vision systems to read road signs (my wife's 2020 BMW X7 appears to do this), backed up by map data from the nav (think Waze, Google maps etc). It makes sense to have that information available to driver since there are a lot of roads in the US that don't have regularly posted or clear speed limit signs. What the car does with that data is an entirely different question which the EU appears to be trying to regulate to standardize it.

But my point I was trying to make with the original and follow-up posts is, the system that does the speed limit detection, in at least my '22 Taycan, got stuck and stopped updating the limit. I am concerned that if that system is interacting with the ACC/Innodrive system to modify the set point in the cruise control, that *could* lead to some unexpected behaviors. Yes, the driver should always be monitoring and yes, you should be smart about when and where you use ACC/Innodrive, but in the real world there are a lot of things happening and this appears to be adding one more thing to the task list.

Oh definitely, its potentially dangerous.

Car recognises 50 sign on a lorry, next thing the car throws on the brakes.

Also in the UK we have variable speed limits on a number of motorways, the car incorrectly recognising changes in the limit, could easily lead to speeding violations etc

 

[Jonathan S.]

I think some modern cars are starting to use computer vision systems to read road signs (my wife's 2020 BMW X7 appears to do this), backed up by map data from the nav (think Waze, Google maps etc).

My Taycan is definitely reading the physical speed limit signs. Ditto for my A6ar and i4.

One notable example is Route 2 west of Greenfield MA. Westbound, the sign upping the speed limit from 30 to 55 was damaged during this winter and not replaced. Taycan continued to display 30 this winter, unliked prior winters. But traveling eastbound, the sign was still there, so the Taycan drops from 55 to 30.

Curiously, with on a family roadtrip right now, on long construction zones on I95 in somewhere like GA, SC, NC, and VA (all a blur at this point), the A6ar consistently can’t read the temporary digital speed limit signs with the numbers in red LEDs.

The Taycan among those three models though is unique for occasionally getting stuck on a speed limit with no further updates until the car is turned off for awhile.

 

[RSouthern]

The Taycan among those three models though is unique for occasionally getting stuck on a speed limit with no further updates until the car is turned off for awhile.

I was hoping the "stuck on an old speed" issue was just me and a one time issue. This isn't encouraging. Maybe time to let NHTSA (or whoever tracks these things) know (if there's anyone left there)?

 

[Jonathan S.]

I was hoping the "stuck on an old speed" issue was just me and a one time issue. This isn't encouraging. Maybe time to let NHTSA (or whoever tracks these things) know (if there's anyone left there)?

Whenever anything goes wrong with your Taycan, it's not just you.
Even when I hit that racoon and caused ~$10k of damage, I called an indie (yet authorized) Porsche collision repair shop (when my insurance carrier was balking at some aspects of the dealership's estimate), and ... "Oh, I just finished one of those -- left front hit. I've done a bunch."

 

[David Bennett]

I tried using the speed limit detecting limiter function in order to stay the right side of the law. It's downright dangerous and after a few weeks I turned it off and only engage cruise / limit manually. Speed detection had so many false readings, I found I was regularly over the posted speed limit or, worse, suddenly slowing down in traffic on a fast road due to a spurious detection of a lower speed limit. Worst example was where I was on a busy 70mph road and the car suddenly tried to move me to 20mph.

 

[W1NGE]

I think some modern cars are starting to use computer vision systems to read road signs (my wife's 2020 BMW X7 appears to do this), backed up by map data from the nav (think Waze, Google maps etc). It makes sense to have that information available to driver since there are a lot of roads in the US that don't have regularly posted or clear speed limit signs. What the car does with that data is an entirely different question which the EU appears to be trying to regulate to standardize it.

But my point I was trying to make with the original and follow-up posts is, the system that does the speed limit detection, in at least my '22 Taycan, got stuck and stopped updating the limit. I am concerned that if that system is interacting with the ACC/Innodrive system to modify the set point in the cruise control, that *could* lead to some unexpected behaviors. Yes, the driver should always be monitoring and yes, you should be smart about when and where you use ACC/Innodrive, but in the real world there are a lot of things happening and this appears to be adding one more thing to the task list.

Cars with cameras have been reading road signs for a number of years now - Taycan since launch 2020 - and other brands before so absolutely this is nott a "new thing".

The issue is reliable data sets, poor mapping, poor signage and poor road markings.

The standards were in place some years ago however that doesn't take into consideration all the dependencies not least the myriad of bodies who control the roads.

Sponsored