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Speed limit sign on the dashboard oddity.


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I noticed a while ago that when the limit changes from 40 to 60 on one road I use regularly sometimes the dashboard will show the 60 mph sign but sometimes it will show the derestricted sign.

Wonder why and has anyone else noticed this?

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Not noticed that myself but one oddity I've seen is when coming down the A422 toward the M40 the 'speed limit' indicator on the dash shows the blue motorway symbol. It's very consistent.

I assume it's reading this road sign but it makes no sense to show that symbol. I'm on the A422 and 99% of the time I'm going straight over the top of the M40 and into Banbury.

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I'm guessing it uses historical data. But I remember someone said before it scans the road to determine the speed limit. But I'm in London and it's probably 80-85% correct, due to consiste changing of speed limits (30 down to 20mph)

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Yeah 70-80% is about how I'd rate the accuracy of mine as well. This is why I'm dreading the newer cars which have enforced speed limiters in them - If the current system's accuracy is anything to go by we're going to see more accidents, not less, when you get massive speed deltas due to them limiting the vehicle to the wrong speed...

Some of the speed limits are already ridiculously dangerous (One road I regularly go down was made a 20 zone for no reason, and is far too wide to be a 20mph zone. I did tried to obey it at first but quickly found people would just overtake me at any opportunity; When a bus overtook me that was the final straw!), but to have them overriding a driver's common sense with the wrong speed I just can't see ending well...

But as I've said, I am utterly utterly against all these systems - They just make good drivers worse, and unless the goal is to abolish the driving licence, the right thing to do is to improving drivers with training and banning the dangerous ones permanently instead of giving them a slap on the wrist.

After all, these systems are not going to do anything to stop dangerous drivers, as they will either disable them somehow or just get cars that don't have them, while it potentially puts the rest of us in danger when the car overrides us in an emergency situation (The T-junction emerge problem in my Mk4 is a perfect example of this!)

 

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As far as I know, the speed limit dash symbol uses the traffic sign recognition camera system. When going along some of our local 30 limit roads it displays “20” - as it seems to have seen those signs leading into side roads. It is far from reliable and there is no way I would want it to be dictating the maximum speed of the car. 

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I agree it's totally unreliable. on a single carriageway road near me it shows 40 on one direction & 30 on the other. it's been 40 ever since I've lived here which is 35 years. On another stretch where they've just reduced the limit of shows 30 as it passes the new sign then clicks back to 40, the old limit, after a car length. 

I wish I could update the system.  As Cyker says with the new auto speed limit coming in (maybe?) it'll be a disaster unless proper data is programmed in, ams whose going to do that in a timely manner 😫.

I also have the de restricted sign sometimes pops up, that seems totally random, different times & places. I think it's only this year I've seen it so perhaps related to the last nav update? 

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Jiff, as Chris said in the post prior to your last one, there is a camera reading road signs. From outside your car look top centre of the windscreen, you will see the camera. Keep that area of screen clean. So, if a camera is reading speed limit signs it needs to be able to see them. I find some signs are either dirty and not just clear enough, or even not placed where a moving camera can see them easily ie too far back or been movers around. Remember that some signs will have been in place a lot longer then camera reading systems and simply could be “in the wrong place” for camera recognition. You will also get the camera picking up road signs n the back of foreign trucks/trailers ie 100, which is obviously km/hr.

If new legislation means you have concerns about future legislation dictating speed of your car due to misreadings, rather then just posting on here, write to your local MP and also Dept of Transport, explaining concisely your concerns.

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9 hours ago, Chris Nutt said:

As far as I know, the speed limit dash symbol uses the traffic sign recognition camera system. When going along some of our local 30 limit roads it displays “20” - as it seems to have seen those signs leading into side roads. It is far from reliable and there is no way I would want it to be dictating the maximum speed of the car. 

It seems to use a combination of camera and (if fitted?) sat nav. There's a road near me that had its limit raised a few years ago and unfortunately despite my best efforts I've not yet managed to get the map data properly updated(*). So the car usually thinks it's a 50 mph zone. However sometimes when turning on to it from my estate the car will catch sight of the NSL sign and for the first few hundred yards will show it as 60. Coming in the opposite direction it will detect a drop from 70 mph to 60 (A43 dual carriageway to A422 single carriageway) even though there is no signage at all so that shows it responds to the sat nav.

I actually thought this was bad signing but it turns out that the law was changed a while back meaning that turning off one road to another doesn't require a speed limit sign if both roads are NSL. Unfortunately I think it adds to the confusion because locals still think it's 50 mph at that point.

(*)I think someone reverted most of my last change 😞

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4 hours ago, Jiff said:

I wish I could update the system.  As Cyker says with the new auto speed limit coming in (maybe?) it'll be a disaster unless proper data is programmed in, ams whose going to do that in a timely manner 😫.

You can update the map here.

However I don't know when Toyota take their snapshot and as I note above I think someone once reverted most of the changes I made. They also broke navigation to Staverton Golf Course by replacing its address with the postcode leading to my car thinking it was in the middle of a housing estate in Daventry.

If you don't fancy the hassle of using the map creator, let me know the road and I'll fix it for you 😉

And two more issues with the camera system:

* A75 - there are separate speed limit signs for HGVs but all the car reads is the number so it will show a red 40 as you drive along at a perfectly legal 60.

* Countdown speed limits - the car is colour blind so it will show you as being in a 30 while you're still a couple of hundred yards out.

Thinking about it the camera always has to take priority so that the car can show temporary limits but I assume that if your car doesn't have sat nav it won't be able to get limit information from that source.

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I assumed that the information about the speed limits came from the sat nav system never thought about a camera picking up the actual sign.

But that still doesn't answer why sometime it shows one sign and sometimes the other.

Next time I'm out I'll check out what the signs are ie 60 or derestricted.

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It does depend on the car, as some use cameras and some use a combination of GPS and camera, but usually the camera overrides the GPS. I don't think GPS-only would work, esp. now that these stupid Smart motorways are a thing, as they wouldn't get updated often or quickly enough.

My top-spec Mk4 Yaris doesn't even have satnav!! :laugh: 

 

The system does need some common sense drummed into it tho' - My favourite one is when my car suddenly thinks the speed limit is 80 or even 120mph for no reason, which has happened a couple of times! Often it's because of foreign lorries, but I have had it happen before where I've been unable to spot what triggered it!

 

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On 12/21/2021 at 8:47 AM, Catlover said:

Jiff, as Chris said in the post prior to your last one, there is a camera reading road signs. From outside your car look top centre of the windscreen, you will see the camera. Keep that area of screen clean. So, if a camera is reading speed limit signs it needs to be able to see them. I find some signs are either dirty and not just clear enough, or even not placed where a moving camera can see them easily ie too far back or been movers around. Remember that some signs will have been in place a lot longer then camera reading systems and simply could be “in the wrong place” for camera recognition. You will also get the camera picking up road signs n the back of foreign trucks/trailers ie 100, which is obviously km/hr.

If new legislation means you have concerns about future legislation dictating speed of your car due to misreadings, rather then just posting on here, write to your local MP and also Dept of Transport, explaining concisely your concerns.

Thanks Catlover, I know about the camera and reading dirty signs, the road in question with different speed limits each way its 40mph so there are no repeaters. It picks up the 40 sign but then drops to 30 but only in one direction.

Good idea to write to my local MP, I'm sure Teresa will get something done 🤔. I may drop the DoT a line as well.

I did look at mapcreator once and may do again as AndrueC said. I wonder how it works changing speed limit information, I can't believe I'd be allowed to do it without moderation otherwise it'd be a hackers paradise. I'd rather be able to change it locally on my car, but may give it a go. 

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1 hour ago, Jiff said:

I did look at mapcreator once and may do again as AndrueC said. I wonder how it works changing speed limit information, I can't believe I'd be allowed to do it without moderation otherwise it'd be a hackers paradise. I'd rather be able to change it locally on my car, but may give it a go. 

It seems to be a free-for-all as far as I can see. I have made several changes including one in Banbury that significantly altered the routing when crossing town (the map thought a road was still open but it was actually blocked off to vehicular traffic). If there is any kind of moderation it's behind the scenes. Responses to my questions in their forums have been patchy. I queried an issue with the M54/M6 junction (it treated each tiger tail as the M6 leading to very late turn advice) and received a positive response and the issue was fixed.

But other queries have gone unanswered.

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