Our Kadjar gives us a warning noise when we are exceeding the speed limit. Permanent speed limits I can understand. I assume programming a satellite?
What I don’t understand is how it knows to warn us when we are going through temporary restrictions - typically road works - when a speed that is normally (say) 80, brought down to 50.
(You can tell I’m bored with the heat and still a week to go!)
Anyone know? How do they do that?
Speed limits definately do not come from satellites. Your car camera can recognise road signs such as speed limits and your navigation software may also interrogate an online database which is easily updated.
Its the world of information, which service they use though, Garmin, Google etc.
Yes sounds like it’s from the sat-nav to me, although I’ve never used a modern integrated in-car system, I rely on Google Maps on my phone.
I’ve always assumed the lower speed limits on sat nav came from a database. My car sometimes flags them up when the work has finished and the speed limit should be back up to 80 or whatever.
It can be very handy. My car can set cruise control to stick exactly to the posted speed limit. (which sometimes drives more impatient drivers behind, mad). There is one stretch of road near me about 100 metres long, one side only where it thinks the limit is 70 not 50. The unexpected increase in speed can be rather alarming.
Clever. Although I do that manually anyway, it only works if I’m paying attention. 
No so sure Mik. Our car can flag speed limit changes when there is no sign, so it can’t come from the camera.
Reading the sign is only one option. Info from an online data base is another possibility…
You could try driving in reverse to your local town and see if it speed limits are identified - if they are not then it is the camera!!!
(Alternatively you could put masking tape on the windscreen where the camera is just below the rear view mirror and see what happens when driving)
Nope nope nope…all wrong.
Renault and Peugeot and Citroen all stuff a very small and cute marmot into the grille thingy.
These marmots are specially trained to read the road, and emit a small ‘eeek’ sound your car recognises and turns into a more human friendly ‘bong’ sound.
Now, you might wonder how this is allowed or possible?..me too, but they are free to roam and do well eating insect splat off the grille and even cooked, on the grill if you get my drift.
That makes sense.
Your satnav is continually running in the background sending speed limit info to your beeper from the database.
Waze does it too. So infuriating if you do not shut it down completely.
Yes, but how are the temporary speed limits getting into the database?
Does it mean that every time there is a fauchage or a roadworks someone is sitting at the side of the road programming it into the google (or whatever) database? And if it isn’t satellite, how is the info from Google getting to our Kadjar.
I need more info.
Yep, our Civic took info from the camera and from the GPS. On occasion giving us contradictory advice 
In the UK, there is a procedure for changing the speed limit (which you would expect, of course). It’s done in anticipation of the change. I imagine part of that procedure is notifying Garmin etc of the change. Roadworks are commissioned, authorised, planned in advance of the tireless activity we see.
I suppose it’s the same in France.
I’m not sure the word “planned” is appropriate here, in respect of UK road works at least.
Currently there is a month-long road closure on my usual route into Guildford, due to replacement of gas pipes. For the first two weeks of the operation the best alternative route was closed as well.
The exact same stretch of road currently being regassed was closed for two weeks a couple of months ago for the installation of speed bumps and 20 mph signage.
The diverted traffic is all coming through my village along a very narrow road, including HGVs who are blindly following their satnavs and ignoring the large “unsuitable for HGVs” signs.
Plus there is another set of roadworks further along towards Guildford with temporary traffic lights which comprises two holes on the grass verge but nobody working in them.
This is how it is meant to happen, yes, but of course sometimes it does not…much the same way that utility companies do not communicate amongst themselves as oft as they should… 
Waze offers the driver or passenger the opportunity to enter details of roadworks and reduced speed limits thus updating the database.
In addition, by default, most navigation systems report your speed (anonymously, allegedly) back to the database. Add a bit of AI and it can easily work out that nearly everyone slowing to 90 in a 130 zone means that a temporary reduced speed limit is in place.
I’ve wondered about Waze. Is it legal for a driver to be entering information while driving? I don’t use Waze by the way, I find it too distracting if I’m at the wheel.