There’s a road that was designated as closed for a while, then residential, now tertiary. Tertiary is correct, it’s open to through traffic.
However, in the map view, the section (or some of the section) that was drawn as narrow when tagged as residential is still being drawn narrow. A nearby tertiary road is drawn wider.
OCD, yes, but is this a bug or some kind of expected behavior?
Have those apps updated their data since you updated the road classification? Generally it takes quite a while for changes to feed through to all users.
I’m not sure exactly what map style the first screenshot is from - is it a locator map within the editor? Again, it is probably just a matter of waiting for updates.
The default map at openstreetmap.org is unusual in the way it tries to reflect changes in near real time (cache issues aside). As @Fizzie-DWG said, it looks like a constant width there (screenshot below). With most maps, a little patience is needed.
Okay. The map with the annotation “Both are tertiary roads” is from openstreetmaps.org directly: Link to page
It’s what I think you are calling the editor locator.
The snapshot you provided doesn’t show the location where the transition between thick and thin lines occurs; that’s here:
I eventually managed to reproduce this view. I had to change the background to “OpenStreetMap - Standard”, which I never use as a background myself. (The choice of background is not encoded in the link). I’m not sure exactly where those thick black lines come from, but I think the same applies - they are probably not fully up to date.
I think if you exit the editor and view the default map you should see the whole road with the same width.
Yes, it’s the OpenStreetMap (Standard) background, with Locator Overlay enabled, within iD editor.
As mentioned already, you should see the normal map outside of the editor, just on openstreetmap.org without going into Edit mode. Or disable the Locator Overlay when using that background in the Edit mode.
In the screenshot, I put the bing Imagery as the background, as it is not related to OSM-carto by itself, but to the layer iD adds when zooming out (as @jimkats says, this is called the Locator Overlay).