Major navigation issues with Garmin 1030 and 820 devices

I have had the same issue with the supplied garmin maps routing me 140km with 2000m of climbing instead of the 50km flat obvious route. I tried all sorts of settings which made no difference.

Switching to another OSM map gave better (predictable) results. 

The reason is not the 1030, it lies in the loaded maps and the layering of those maps.  Not all OSM maps perform exactly the same either, it will depend on where they are downloaded from. 

None of this is garmin's fault.

ps. I wouldn't travel anywhere I don't know without having at least 2 maps to use

The simple answer is the Garmin doesn't know they are decent roads for cycling but It should know that cycling is permitted therefore should use them if it provides the quickest/shortest route to a destination as configured in the navigation settings based on the configured avoidance settings. The trouble is for Road Cycling Garmin deems some roads are not permitted by default and avoids them with no options available to allow their use. 

Using the Garmin I don't believe it's possible to navigate back to the start using your recorded route as there's no way to reverse it. You only have options to use the current course or most direct route. Neither of which will take you back the way you came.

Most uses for back to start would I imagine be to get you back quickly because you were either running out of time or something went wrong with your day so you'd probably want to use the the quickest route possible. Because of the restrictions imposed in the Road Cycling routing it wouldn't take the quickest permissable route

Imagine you are riding your pre planned course in an unfamiliar area when something goes wrong & you need to navigate to the nearest bike shop or heaven forbid a medical centre. What would you use if you won't trust your Garmin to get you there? 

with just "unpaved roads" selected in route avoidance it is 39.5 miles. If I then disable the Garmin maps and enable the OSM maps for the same jouney with the same option set it's 3.6 miles on the roads I would expect.

Hi, I have just tried one of my "problem" routes in GC and that has the same issue as both my 820 and 1030 devices so I guess the problem is a Garmin map issue and not a device defect. The crux of the problem is the Garmin maps that all my devices use.

The UK A roads are classified as "trunk" roads. In the US, trunk roads aren't places where people cycle (either because it's illegal or very unpleasant).

Most ways in OSM aren't explicitly designated as allowing or disallowing cycling.

That means assumptions must be made.

The assumption is that trunk roads don't allow cycling. That works in the US but doesn't work in the UK.

OSM default is to allow cycling on highway=trunk

https://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions

How Garmin interprets this data and publishes it in its maps and how the Edge responds to the data is a subject to another post i've made in an attempt to get to the bottom of this annoying problem.

Thanks for your opinions.

Thanks for the explanations. Just a small misconception I should correct, that is not all A roads in the UK are designated as Trunk roads in fact only a fraction have this designation. Regardless of this, cycling is permissible whether they are trunk or not though there are many I wouldn't cycle out of choice.

I had a look at the OSM tags for the A roads near me and only one is tagged as highway:trunk the rest are either tagged as highway:primary, highway:secondary or even highway:tertiary.

I do agree however that Garmin should compile it's maps differently for the locale where they are used, despite my best efforts at ahem 'reaching out' to Garmin support regarding these navigation issues I've just been fobbed off case closed.

From your explanations regarding US roads it does appear that my rather tongue in cheek suggestion that Garmin has designed the Edge & mapping around the US market has an element of truth & users from other regions have to live with inferior navigation as a result

"A" is just part of the name. I'm not really talking about the name of the road.

The routing is based on the road classification (not the name). Looking at the OSM map for England, it appears that quite a few A roads are designated as "trunk" (but not all of them).

Primary, secondary, tertiary A roads shouldn't be a problem.

Routing for cars is easy. Routing for cycling is much more difficult. People also have a wider difference in opinion about what is "suitable" for cycling.

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A clarification:

The routing is based on the road classification in the map (*.img) BUT the name (or other information) in the source data could be used to change the road classification before writing the data to the *.img file.

It appears that A roads (trunk or primary) are classified as "major highways" in the Garmin (and some other) maps.