They say you’re never too young to learn.
Sometimes one needs to ask for assistance, which I did through a ‘help post’. Learning that a UK section may have saved me from asking the world.
I’m conscious of not repeating my original post so in short.
Sat Nav directed me to do a U-turn on a 'town dual carriageway when signage prohibited.
Can anyone direct/assist me in resolving this matter
Hopefully, I have given you enough to start
You will note the issue is in Redruth, Cornwall
Thanks
Where were you going from & to?
I was driving up from the mini roundabout, access roundabout to Tolgus Place, towards Barncoose roundabout (I said, dual carriageway as the mapping shows two separate lanes, a cycle lane).
There are two sets of traffic lights, the first set approached from the direction I was travelling, is to the right, and there is a filter lane to turn right.
The road is not designated but leads to Tolgus Mount and Illogan.
This is where I was directed to make a U turn.
Thanks for your help.
Sorry, but that’s totally meaningless to me! 
Could you please have a look at OpenStreetMap, move your start & finish pins to the right places & repost a link?
Thanks!
Graeme, Please see attached link -
I hope this is more clear
It is, thanks!
Unfortunately though, it didn’t help with your problem!
I’ve just tried all 3 of the built-in routers & they all went straight through those traffic lights.
Looks like it may be a bug with whichever router you were using? 
Sorry I couldn’t help further.
Thanks for trying, I’m a little confused when you say router. If you are wondering about my setup
My old smartphone with no SIM runs from MIfi router
One thought on my destination, Camborne Retail Park
Was probably why sat nav wanted to take me back to the 'slip road roundabout (Avers) then down the A30 and off at Tolvadon.
Again thanks for trying, next time I’m that way ill give it another go.
Rgds
Pete
Hi Fred
I am not familiar with Mifi router but a question.
When was the map data last updated?
Cheers Phil
Hi Phil,
The app was installed early this week, so I guess it updated itself, but will check.
I linked an old smartphone wifi to the Mifi and has virtually all the functionality of a smartphone. Linked to the van head unit by Bluetooth, I’m not at the point of ‘a smarthead unit’, but if I had I would run it from the Mifi
Mifi, is by virtue, a mobile phone with SIM( its a small palm sized box) with an amplifier on the roof
(other brands available)
Hi Fred
I misunderstood you there, so Mifi is the OS?
What app are you using for navigation?
The thing to be aware of is apps update their maps at different times, most only update once a month, others are less frequent. When you installed you will have got the apps last update from OSM, not the state of OSM when you installed it
Cheers Phil
Phil, sorry for the to and fro, I have learnt so much already.
The app is ‘OsmAnd’. Map Updates for mappers, on the app on my phone, used.
The Mifi yes (driving Android ?), and that was updated (reinstalled early this month)
A Mifi could be described as a mobile phone without a screen or keypad, it works either separately on in conjunction with a rooftop aerial, which improves the signal inside of the van. The Mifi is mobile (independent of the van) and can be carried on a hike for additional signal. You pay for a SIM in the same way as phone contract works.
Many thanks Pete (Fred)
Interestingly OSMand on my phone does not suggest a U turn at that
point, it sends me to the next roundabout.
However I have added a turn restriction which will be valid next time
your maps update. Early June for standard OSMand or now if you have
OSMand+>
Cheers Phil
Thanks Phil, will also check, like it was suggested, a thrip…
There’s been confusion from that question that I don’t think got spotted.
Saying you used osmAnd was helpful enough.
If you use the osm.org website, after selecting transport type you’ll see there’s a drop down of routing engine options (Valhalla, OSRM, GraphHopper). They’ll all use different programming/logic, and possibly different parameters, to decide which route to take.
I’m not sure which routing engine osmAnd uses (possible it’s own?). If you get into the settings (Driving profile, Navigation Settings, Route parameters, Routing Type) you can change it to several options (A* 2-phase, A* classic, HH x Java, HHx C++) although I think that’s more about how the routing code is procesed. I would advise not to change it, I’ve only done so when I’ve had severe performance issues and navigation calculation would hang on about 80% but never finish.
Anyway, it seems nobody was able to recreate this. Hopefully that’s because the OpenStreetMap data got changed/fixed and it will be fine when osmAnd updates.
Hello Fred,
I come from Germany and my last visit to Cornwall was over 15 years ago, but I still have a question as to whether I have understood you correctly:
Your original starting point was in Scorrier and you wanted to go to the Camborne Retail Park.
You got lost in Redruth and took the wrong exit at this roundabout.
Your router (OSMAnd) wanted to route you like this (on osm.org routing with Graphhopper):
The fault at the point you highlighted seems to have been fixed, but the same problem seems to exist at the next junction with the Tolgus Vean.
However, @trigpoint edit seems incorrect or incomplete to me. At the marker location, according to the aerial photo, there is a left turn lane coming from the north to the west (only u-turn is not allowed). I miss this in the OSM data
But perhaps I am mistaken and the situation otg is now different from what is visible on aerial photos.
I have now fixed that one. The no U-turn sign can be seen on mapillary.
Thank you all, I appreciate the speedy response and the solution.
