I have created courses, but I haven't tested those yet. In Google Maps navigation it didn't take account on one direction roads in Mallorca.How about Garmin.
Try looking at the Course on the Edge and see what it comes up with for the Course in question
Garmin connect maps appear to I have had no issue in the UK
“I have create courses”?
On the device or on a website?
The device won’t route you the wrong way on one way streets. But the map has to have the correct information about the road.
The web-based planners won’t send you the wrong way either.