Most road types in OSM are “assumed paved” in developed countries if not explicitly stated otherwise. But sometimes people map roads from aerial imagery without actually going there and don’t fill in the surface type. Could you give a few examples?

https://cycle.travel/map?from=Kuld%C4%ABga&to=Liepaja&fromLL=56.9685757,21.960778&toLL=56.5048435,21.0070903

Km 5⇒15 of this are 100% dirt trails.  After Snepele, the turn cycle.travel wanted me to make was also a dirt trail.  There were many others in previous days, but I'd have to go sync up video and gps tracks to let you know exactly where, lol.

Or I should say, just before Snepele:

https://www.google.com/maps/@56.850822,21.9543658,3a,75y,239.69h,86.42t/data=!3m7!1e1!3m5!1sbbLQsjEd36fHGqmMHuhnWw!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DbbLQsjEd36fHGqmMHuhnWw%26cb_client%3Dmaps_sv.share%26w%3D900%26h%3D600%26yaw%3D239.6918467884383%26pitch%3D3.579913011447445%26thumbfov%3D90!7i13312!8i6656?coh=205410&entry=ttu

^ is the branch at km16, and 

https://www.google.com/maps/@56.8528402,21.9528377,3a,75y,64.33h,78.86t/data=!3m7!1e1!3m5!1s8xTcHsb9xoVbXwLgG--ZcA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3D8xTcHsb9xoVbXwLgG--ZcA%26cb_client%3Dmaps_sv.share%26w%3D900%26h%3D600%26yaw%3D64.32526072925054%26pitch%3D11.140228490746352%26thumbfov%3D90!7i13312!8i6656?coh=205410&entry=ttu

^ is where I came from just before that.  While it looks okay right there, a few hundred meters back it's basically two cycle tracks with grass in between.

Anyway, the point is, definitely not paved ;)

And if you look at GPS around there, you can see almost nothing is paved, but cycle.travel thinks most of it is

*satellite, not gps

Thanks! I’m away from home at the moment so not able to do a proper investigation right now but will do so when I’m back. 

As suspected it’s an OpenStreetMap data issue – these are marked as normal minor roads as paved roads are in the rest of Europe, it’s just that no-one has marked them as unpaved. It looks like the Latvian mappers need to put a bit of attention into that!

I don’t think there’s a whole lot that c.t can do about this unfortunately – taking the opposite approach, and assuming that minor roads in Latvia are unpaved, would mean that the routing would gravitate onto busier roads instead. It probably just needs a few days’ work in OSM to fix the worst examples.

I just toured through most of Latvia, and the area I gave was just an example, I actually started ignoring CT's routes in Latvia and just following Google Maps' driving directions as those "busy" roads are not even remotely busy.  Educated guesstimate, half of all the roads in the country outside of cities are marked incorrectly.  There's just nobody there to care I guess, lol.

Yes, lots seem to be wrong, including even roads marked as highway=primary – even the US (which is notorious for untagged, unpaved roads) has its major roads correctly tagged. I don't think there's anything c.t can do about this unfortunately.