Clarification on Avoidance and Routing

Major Highways -> Motorway and Trunk. Not primary. Assumed not usable by cyclists unless it's explicit that cyclists are allowed.

Paved -> paved, concrete, asphalt, sett, cobblestones or assumed paved (if not specified for certain roads like primary/secondary/tertiary/minor/residential/service). "Tracks" are unpaved (aren't considered roads).

Narrow trails -> Trails (not roads). Probably, not wide enough to drive on, Unpaved.

"Tracks" are wide-enough to drive on (like ways for agricultural equipment). Like a path wide enough to drive on. Not "narrow". 

Hi and thanks for your input.

Anyone from Garmin able to clarify??  Please. :-)

With respect to Narrow Trails, what do you mean by "Trails" as there is no such tag in OSM?  Do you mean track?  If so then most tracks are unpaved anyway apart from those tagged as grade1 tracks.

I've experience some weird routing decisions here in the UK which I believe are due to the propensity of small roads being tagged as Minor/Unclassified.  

https://wiki.openstreetmap.org/wiki/Tag:highway=unclassified

These may or may not have an implied "unpaved" tag.  Can i ask what experience of routing on Unclassified Roads you have in your country?  Do they work OK for you or do you find that the Edge avoids them?

Thanks, Dave.

One of the problems in the UK is that when using the Road Cycling routing mode & navigating to a place the Garmin will take convoluted routes to avoid perfectly usable 'A' roads. Even if that road would result in the shortest route to the destination, which is the setting I use. 

I guess this is also due to the way A Roads have been classified in the Garmin maps 

I've taken to using the Motorcycle routing mode & 3rd party OSM maps (because the garmin maps don't allow motorised routing modes). The only downside to this is the turn prompt pop-up appears about 700m before the turn instead of 200m, which is no doubt to account for the additional speed of the motorcycle  

One of the avoidance settings for motorcycle/automobile routing is not available in the Road Cycling routing mode, which garmin seems to assume by default are non cycling roads & prevents their use

It's very unlikely that you will see a reply from Garmin.

Minor and unclassified aren't the same thing. 

You shouldn't see problems with "minor" roads.

I don't know what Garmin does with "unclassified" roads. It seems Garmin ignores "service" roads unless they are tagged to allow cycling.

I do a fair amount of OSM editing. I rarely see unclassified roads. 

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"With respect to Narrow Trails, what do you mean by "Trails" as there is no such tag in OSM?  Do you mean track?  If so then most tracks are unpaved anyway apart from those tagged as grade1 tracks."

"Trail" is a common word.  What do you see "trail" to mean? I doubt you think it means road or "track" (as OSM uses that word). OSM does have "path", which is a common synonym for "trail".

In the real world, "paths" are sometimes paved and "trails" are nearly never paved (at least, in the US).

OSM uses "footpath" for paved paths (something that would work for a wheelchair) and "path" for trails (it appears).

"Track" is less common (but OSM indicates what it takes as the meaning). A paved track would be an odd thing indeed. Assuming that they are unpaved makes sense.

It appears many (if not most) ways in OSM don't include the surface type. That means, to be useful, the surface has to be assumed. 

The issue with "A" roads in the UK is that they are classified as trunk roads. As I said, Garmin assumes trunk roads don't allow cycling by default. In the US, trunk roads are nearly motorways. 

Unless the UK allows cycling on (nearly) every trunk road, the only reasonable assumption Garmin can make is that they don't.

It seems like the A road issue is a data problem.

People should update the data for A roads that allow cycling.

I would hazard a guess that nearly all A roads permit cycling with the exception of a couple which are designated motorways and have an (M) suffix.  Ie A1 (M).

Some A roads are classified as trunk roads some aren't, though regardless of that classification cycling is permitted on both types.

I guess I'll have to work out how to amend the OSM data onsome of the roads near me and see how that affects the routing on future map updates 

The "A" has no special meaning in OSM (it's just part of the name of the road). So, "nearly all A roads permit cycling" doesn't mean anything with respect to routing.

It's the "trunk" classification that is causing A roads not to be used for cycling. That's (likely) due how "trunk" is used in the US (as a "nearly a motorway").

If an appreciable number of A roads disallow cycling, assuming they all do would be another problem.

Garmin assumes left-hand driving in the UK So, it could assume UK trunk roads allow cycling (but I wouldn't expect they'd ever choose to do that).

Trunk implies surface=paved only.  You can cycle on this type of route, you just might not want to because of the busy nature of the traffic.  Its a case of what Garmin chooses to do based on the routing mode and avoidance settings.  And that's really what my questions was about.

https://wiki.openstreetmap.org/wiki/Tag:highway%3Dtrunk

Motorway implies access=no, motor_vehicle=yes, oneway=yes, surface=paved.

https://wiki.openstreetmap.org/wiki/Tag:highway%3Dmotorway

You shouldn't edit the map data to frig the routing.  The routing should interpret and use the map data correctly.

• "Trunk implies surface=paved only."

No, that's not the important thing about "trunk". From your link, this is more significant:
Use highway=trunk for high performance or high importance roads that don't meet the requirement for motorway."

• "You shouldn't edit the map data to frig the routing."

You wouldn't be "frigging" the routing (that would be really bad to do).

Since the allowance isn't explicit in the data, the allowance has to be assumed,

• "The routing should interpret and use the map data correctly."

There isn't "data" (there's only an assumption). What is a correct assumption in the UK wouldn't be correct in the US.

In the US, it would be inappropriate to assume "trunk" roads as allowing cycling.

There is a difference here between preferences/avoidance's and entitlements.

The OSM access=* and specifically cycling=yes (either implicit or explicit) defines the entitlement to use a certain way.  The Garmin routing engine uses the preferences/avoidance's to chose which of the entitled ways it 'should' use (well should anyway #sigh).

If you loop back to my original question you will see it was not about entitlements but about preferences.

Narrow trails is still a mystery to me.  No such thing in OSM as a trail despite it being a "common" name.  In terms of cycle highway use the food chain would go as follows.

Motorway, trunk, primary, secondary, tertiary, unclassified, track, path.

Yes, the word 'unclassified' is a historical artefact of the UK road system and does not mean that the classification is unknown.  We have loads of rural roads tagged as unclassified in the UK.

There is no such thing as an assumption here, just data and an algorithm to interpret it.