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Currently on holiday in a spanky new Peugeot 5008 hire car and I've noticed the speed limit indicator changes in places where there aren't any speed signs.
Typically, I'll see a speed limit sign for, say 50km/h so trundle along at that speed, then randomly the in car indicator will show something higher (eg 70kmh). In some cases, there is definitely NOT a sign indicating the speed limit increase.
This doesnt always seem to coincide with town/village boundaries and only seem to be "problematic*" when the speed limit goes higher (when speed limits reduce, it is usually well signposted)
*Problematic for locals stuck behind a dawdling tourist keeping to (lower, imaginary) speed limits.
(This is Croatia but I seem to remember similar in France and Spain when I had hire cars there, but I'd assumed I'd just not noticed a speed limit sign post...)
My solution is to ignore the car display or sat nav and comply with any road side signage. It's served me well for 44 years of driving!
It can be built into the SatNav mapping, but is often wrong. For instance there are large stretches of the A9 between Perth and Inverness that Google Maps thinks has a 50mph limit for cars but in reality the NSL applies.
Mines a combination of GPS but mainly it reads the signs, even the variable speed limits on the motorway. Sometimes misses them, occasionally gets it wrong, well over 100 the other day, not great if it's in motorway adaptive cruise mode as it will speed up to the limit.
This remains a bit of a puzzle for me...Google Maps clearly just works off GPS. Sometimes their database is wrong/not updated with recent changes, hasn't been updated for roadworks (or hasn't been updated when long term roadworks have been removed). Sometimes the gps is slightly out and it picks up the 20/30mph road alongside the larger road I'm on.
But it's just a guide so it's fine. I know a load of cars that have cameras supplement this/replace this with sign recognition - including Tesla's FSD mode. But it seems that's not super reliable either (see above).
Yet self driving cars are supposedly imminent?
My mg flashes “40” in the display no matter what rode I drive on, however that’s the least of the issues with such a shite car
I'm assuming local authorities are supplying raw road data to Google which includes a speed attribute for each section of road. But speed limit changes do not always appear to be sign-posted which would make for an interesting legal case if, somehow, you got charged with speeding but cited the cars speed limit indicator (and there is NO SIGNPOST)....In some places I'm also assuming that speed limit x applies everywhere unless a signpost says otherwise but whatever is happening, it's not confidence inspiring!
Our hire car in Italy read road signs but didn't understand /wasn't programmed to read neither the 'leaving a town boundary' signs where the road reverts to a higher limit, nor the secondary white undersign i.e. lower speed limit on motorways in case of rain or fog or lower limits for heavy vehicles. It would only read a circular white sign with red boundary. It's not great. We found google maps better but still not perfect, especially on province rural roads at a lower limit than 'standard', i.e. roads that would usually be 90 kph but signed 70. And Google also misread a lot of stop signs in Italy, where the google streetview reader was clearly reading signs meant for joining roads but applying them to the main carriageway. It's definitely not good enough yet to rely on.
Depends on the car.
many use cameras/vision to pick up speed limit signs. Sometimes a bit too indiscriminately - some angled 20mph limit signs have my car slowing down to 20mph in a 40mph zone locally. Then when it sees the next 40mph sign 10m further down the road back up it goes.
as folks have said, the vision systems are supplemented by GPS/mapping. I’d imagine that for Google-supported mapping that is fed by Google street view image recognition.
without vision I imagine it’s just GPS/mapping data. Way back when one of my MBs had some fascinating beliefs about what the speed limits were in some places based on its few-years-old navigation module.
But speed limit changes do not always appear to be sign-posted which would make for an interesting legal case if, somehow, you got charged with speeding but cited the cars speed limit indicator (and there is NO SIGNPOST)...
Speed limit changes are always signposted (otherwise how would you know?) and there are 'tells' like lamppost spacing if you missed it. If you didn't see the signs it wouldn't make for an interesting legal case, it'd be laughed out of court with a side order of Driving Without Due Care And Attention.
I'm assuming local authorities are supplying raw road data to Google which includes a speed attribute for each section of road
Your assumption is incorrect. Despite guidance from both the Scottish Government and Highland Region, Google are still showing incorrect limits in the Maps app. As already pointed out, drive to the road signs.
I think with the VW/Ford unit it must be a camera/stupidity based system. Quite often on the motorway it’ll display the limit as 100mph, I assume it’s read the 100kmh sticker on the back of a coach or something.
I mean it knows where it is, surely it’s easy to set the maximum speed by country at a minimum.
Are there really cars that actually scan signs on the road in real time? Seems like a lot of high tech to go wrong and they would need a database for backup anyway working straight from GPS.
It seems clear that Google relies on their camera cars having gone along the road and reading signs, and it regularly gets them wrong such as interpreting lorry restrictions as applying more generally. And obviously missing smart changes on motorways, temporary roadworks etc.
My HiLux reads road signs. It shows the limit in the display. I don’t have satnav so adaptive cruise control only works in radar spacing to the car in front. Which is fortunate cos it occasionally picks up 50 signs on trucks on the motorway.
Mrs Scape’s VW has satnav and the adaptive cruise control clearly works off GPS mapping/signal for speed limits. The A9 up to Inverness is its favourite place to show off. Set it at 70 and it’ll drop to 60 when the road changes to single carriageway and back up to 70 as soon as it goes back to dual carriageway.
which is very impressive, except it’ll suddenly slam the brakes on and take you down to 40 or 30 if there’s a parallel road with those lower limits. I tend to have my foot ready to boost it back up as I’m going past certain junctions.
Speed limit changes are always signposted
Well, this is the whole point of this thread and this appears not to be the case where I am on holiday! (Again, not the UK.)
there are 'tells' like lamppost spacing if you missed it.
I'm aware of this rule/convention in the UK, thanks, but I'm not in the UK and this is happening on rural Croatian roads. On a previous holiday in France, the on-dash speed limit display seemed to change at village/town boundaries so at least some logic could be applied and it's relatively easy to figure out where the speed limit changes. But not here in Croatia!
Anyway, it's relatively "safe" in that reducing limits seem to be sign-posted but increasing speed limits it's more random as to whether there will be a sign-post....whatever, the "tech" does not appear to fail- safe
Your assumption is incorrect. Despite guidance from both the Scottish Government and Highland Region,
I'm not in Scotland, or the UK so not sure what the relevance is....
We've just come back from Croatia and found the same in a brand spanking new Toyota, so new that the hire company had not subscribed or enabled most of it's options including satnav and didn't recognise the car at the exit barriers at the airport. I had to walk back for assistance. On the toll roads the dash display kept altering the speed limit even though no road signs showed the limit and we were overtaken by various other road users, however driving in Croatia was an absolute pleasure at this quiet time of year and we found the roads to be excellent and most road users pretty courteous.
Are there really cars that actually scan signs on the road in real time? Seems like a lot of high tech to go wrong and they would need a database for backup anyway working straight from GPS.
As above; yes. Have a look at the top of the windscreen on a range of cars where the rearview mirror sits. There will often, but not always be a large black tapered area, with up to four clear areas with lenses in them. They are cameras for things like speed sign recognition. It’s because of those that if a screen needs replacing because of damage it has to go to a specialist with the appropriate equipment to re-calibrate all of the sensors once the screen’s been replaced. Takes around two-two and a half hours. I used to take cars to Autoglass at Cribbs Causeway, Bristol, which was a nice little jolly because it was an hour’s drive each way, plus the actual work, and I’d spend the waiting time sitting in the nearby MakkyD - four and a half, to five hours away from work, depending on traffic, and getting paid for it! 😎
Mine reads the signs, which was really appreciated on the A75 which has a 40mph limit for over 7.5t vehicles, it read the 40 bit perfectly, shame about the text, but at least I just get a red mph speed display.
Mine reads the signs, which was really appreciated on the A75 which has a 40mph limit for over 7.5t vehicles, i
The "50mph for 7.5t vehicles" signs on the A9 were recently changed so that this doesn't happen.
Combination of camera and GPS on my Vivaro Life. Uses the camera and radar for the adaptive cruise too. Seems to work well. GPS data when no visible signs then camera when it spots them. I've not had any false readings from side roads. Best feature of the van is the heads up display. Speed, speed limit and satnav directions.
Useful in Wales with the 20 zones.
I'm still baffled as to why anyone needs a car to read speed limit signs for them. Surely even in Croatia the posted limits are the ones to drive to, rather than wondering if your system has got it right?
(Even in Wales the big red circles with a 20 inside them are a dead giveaway)
In both our cars you can switch sign recognition off. It’s safer than going along in a 60mph and overtaking someone doing 50mph and then the car not allowing you to overtake safely by going over 60mph
One of our cars can pretty much self drive anywhere. It must use GPS. You can drive for miles with touching the brakes or accelerator. It slows appropriately for bends and roundabouts. Even to the point in eco it does it much slower than in sport
I'm still baffled as to why anyone needs a car to read speed limit signs for them.
This may come as a shock, but many people are not that aware when they're driving and either don't see or don't comply with posted speed limits. The EU has deemed that this is generally a bad thing (some may say that excess speed will make incidents worse or more likely) so they have mandated that new cars are fitted with a mechanism to notify the driver when they exceed the speed limit. To do that the car must be able to determine the speed limit. The driver can also turn off the warning system but it must reactivate at the start of every drive, much to the annoyance of drivers of new cars.
The Vauxhall hire car I had in Majorca last year had this feature. It seemed to be pretty much a random number generator.
As above if this technology is a precursor to self driving cars, we are a long way off yet.
Mine is definitely a bit off at times...I leave the office and drive about 100 yards and the speed indicator suggests it is a 60mph area (as you enter the area it has a 30mph sign), as I approach the end of the road it changes to 30mph.
A roundabout I use regularly has a 60mph on the approach - the opposite side is 50mph. If coming from the 50mph, I enter the roundabout and for about 100 yards it tells me the speed limit is 70mph.
It is a handy piece of information - when it isn't messing about...
I'm still baffled as to why anyone needs a car to read speed limit signs for them.
I suggest you read the op then. I only started this thread as I wasn't sure what tech these systems use, and whatever is being used, it seems pretty useless at the moment (or someone in Croatia is stealing a LOT of sign-posts...)
Are there really cars that actually scan signs on the road in real time?
Yes. This was annoying when driving across France with the adaptive cruise control on and the car would decide to slow down from 130 because it had read the sign on the slip road, or on the back of a truck.
I think it runs on a combo of satnav map, camera (above the rear view mirror) and the distance sensor in the grille.
We had a Renault Australia (or something similarly awful) as a hire car recently and yes, it had loads of these supposedly helpful driver aids that were all utter dogshit. It'd start binging at you at '20 when lights flash', '40 over 7.5T', and the countdown markers to 30 zones. It also told me the speed limit through Banchory was 80mph. Being pushed back into potholes because you hadn't indicated to literally nobody that you were crossing the middle lines was maddening as well. I managed to switch it all off eventually, but that nonsense was two screens down.
Fortunately, all these driver aids in my van don't do stupid stuff. It doesn't grab the steering wheel - just boings if you haven't flicked the indicator (on a motorway), so I can live with the occasional bong on a twisty narrow Welsh road. Some new systems are overly intrusive.
Being pushed back into potholes because you hadn't indicated to literally nobody that you were crossing the middle lines was maddening as well. I managed to switch it all off eventually, but that nonsense was two screens down.
Personal pet hate, lane assist. The HiLux can be switched off on the steering wheel, Mrs Scape's Tiguan has to be disabled before you start your journey several layers deep in the computer menu. A friend's Kia EV6 perhaps had the best compromise. You set a driver profile when you first get in, and it learns your habits. My driver training set in stone not to indicate when you're returning to the left lane after an overtake, and the Kia soon learnt I wasn't going to so stopped wrestling with me. However, if you indicate right to overtake, the cameras on the rear view give you a full picture of the offside lane in the display. Indicate left on a dual carriageway or motorway and it'll do the same. Both mirrors flash red if anything is in your blind spot or approaching you. I was impressed with the tech. The owner told me it'll even help you change lanes if you let it by slackening your grip on the wheel. No thanks!
Mine reads the signs, which was really appreciated on the A75 which has a 40mph limit for over 7.5t vehicles, it read the 40 bit perfectly, shame about the text, but at least I just get a red mph speed display.
This is precisely the problem I've noticed with google maps, which of course isn't actually reading the signs in real time but rather can only be relying on data from a previous trip by a camera car. Which is why I asked if cars really were reading in real time. Happy to be better informed that some do this, though mine certainly doesn't, and I'd expect a consumer-level car to do an even worse job than a google camera-car might (albeit the latter can always be out of date).
I did some of the original stuff on this (Creating the legislation) my name is probably buried somewhere deep in the documentation.
It's based on a mixture of GPS map data (including google) and in-car camera data, there are no rules about the bias/prioritisation between the two but there are various accuracy requirements for sign recognition which vary depending on country and the level of data maturity (from the GPS mapping) and the sign type etc. This increases over time. IIRC it'll top out at about 95% in non-autonomous cars and there is a different scale of errors for autonomous vehicles (errors per million km IIRC).
Google update their map based on vehicle data and their original google camera car data. Mine sends updated map and camera stuff continually (I'm not using "normal" google though), AFAIK most cars running google/AAOS will only send data when there is an error/mismatch between camera and map, depending on which box you ticked when you logged in and what capabilities your car has. I would imagine there is something similar going on with google navi on phones (and apple will probably have a parallel program). Not exactly sure how non-AAOS cars deal with it, as we're fully committed to it, so not looking at anything else.
Croatia probably doesn't have as many data points as somewhere like the home counties or Monaco as there will be an order of magnitude less connected cars using (and updating) the data. So they are relying on other data sources. If they even exist. So they will probably struggle to meet accuracy requirements. It will get better though.
Those companies attaching the cruise control set speed to the camera/mapping function are, in my mind, totally mental.