Bogus Turn Notification

Navigation prompts are triggered by map data that specifically identifies an intersection exists.   Two road can cross, but if the map data doesn't say there is an intersection the navigation device won't know it can turn there.  (Of course this can occur in reality where there's an over pass and no connections between the two roads).  Similarly, if the map data says there's an intersection between two roads when in reality the road is continuous, the Edge can only behave as if there is an intersection and generate a prompt.  As I've mentioned, I've run into map errors on a number of occasions; discontinuity in actually continuous roads, roads misidentified as one way, turns not allowed, surface type misidentified, connections where there were one. etc.. 

The Edge doesn't look at graphical map data and interpret it as does a human.  It can only follow the data in the map, and there's more there than what you see looking at the map on the screen.  Intersections are identified and have associated properties in the map data. 

If a driveway creates an intersection then certainly Garmin is misinterpreting the underlying map data.

On Gibraltar I used a Road Bike profile and the dirt road example was navigated with an MTB profile.

I find the sharp turn warning to be very annoying so I turned that feature off rather quickly after getting my 830.

A driveway connecting to a road is an intersection.  If there wasn't one then you couldn't get into the driveway from the road.  Therefore the driveway has to connect to the road in the map. The Garmin doesn't know that the driveway is a driveway and can be ignored so it can show a navigation prompt if it thinks it is required.

There is no 'driveway' tag is OSM.  You would use the 'service' tag for driveways and you may well want to navigate down other ways tagged as 'service' so you can't really filter them all out.

"Strictly speaking there's an intersection with the driveway of the house right on that corner. OSM has this defined as a service road, which I'm not sure is correct but I'm no OSM editing expert."

Driveways are a subclass of service roads. Service roads intersect with non-service roads all the time. This is normal and common in OSM.

"I think Garmin are misinterpreting the OSM data and have wrongly defined intersections. I wonder also if the activity profile you use affects things... Are you using a Road or MTB profile?"

It's clearly an intersection.

Ignoring intersections that happen to use ways (service roads/paths) has its own problems.

The Garmin has no idea what the intersection looks like or whether it might be confusing to people arriving at it.

I tend to look at the map frequently, which means I often don't need the prompts.

If people don't have the map screen up, shouldn't the device warn them about a turn the device can't know what it looks like?

"Quite a few of the hairpins on the Stelvio do have paths/tracks connecting to them on OSM."

Yes, it's likely the unit is seeing these as nearly right-hand/left-hand turns. Roads like this are not usual at all. It would be hard to "fix" this case without breaking likely breaking more usual cases.

Situations that are easy for humans to discern can be difficult for software to deal with.

"There is no 'driveway' tag is OSM.  You would use the 'service' tag for driveways and you may well want to navigate down other ways tagged as 'service' so you can't really filter them all out."

There is a "driveway" attribute in OSM. Driveways are subclasses of service roads.

If the service road is at an intersection and it might be possible that you could continue on it, it would be proper to indicate it as a turn,

It might make some sense to not notify for intersections that happen to be with driveways.But not all driveways will look like driveways.

"This one is on Gibraltar Rd. The nearest intersection is over two miles away."

As peteb478 pointed out, there's an intersection right there.

It's with a service road but it's an intersection.

"This one is on a dirt road about 0.1 miles from an intersection:"

Again, there's an intersection there too.

https://www.openstreetmap.org/search?query=33%C2%B021%2752.5%22N%20118%C2%B022%2730.8%22W#map=18/33.36458/-118.37522

Keep in mind that the device doesn't know what the intersection looks like.

If the intersecting roads happened to look alike, how would you know which way to go?

You shouldn't be looking at Google maps to explain the behavior of the device (which are using OSM maps).

Looking at Google maps is fine. You just can't just look at Google maps. You have to be sure to look at the maps the device is actually using.

"yes every hairpin triggered a navigation prompt but I don’t really get why"

www.openstreetmap.org/search

I think the hairpin curves are an odd/extreme case (especially there). I don't think it's reasonable to expect that the device will handle that situation "perfectly".

I think some of the issues people are describing are the result of unreasonable expectations.

In my opinion, the only real way of using the Garmins is to think a bit more.That is, people have to be more involved in the navigation than they quite realize. (It takes some practice/experience to do that but it becomes fairly routine after a while.)

"Maybe I could have disabled prompts or something."

For this case (especially), that would have made a lot of sense.

Surely they could deduce that it's a driveway since it doesn't have a street name. Why is that one driveway so special?

Driveways are rarely announced. So, it’s not a common issue.

Most driveways aren’t at abrupt turns. They don’t get announced just like other streets that at right angles to your route.

Why is this one driveway being announced such a problem for you?

The navigation is designed to work without names. 

The routing would work on tracks and paths that don’t have names. 

I’ve ridden in places were the road doesn’t look much different than a driveway.