Highways abuttered by boundary=protected_area have poor legibility

[btwhite92]

Expected behavior

Highways should maintain consistent legibility with respect to themselves at each zoom level.

Actual behavior

Highways bounded by boundary=protected_area/leisure=nature_reserve have poor legibility at mid and high zooms:

This is especially a problem with minor roads - here's an example where one has been made almost entirely illegible:

Suggested fix

• Render highways above protected_areas/nature_reserves/... at the expense of clarity of boundary locations along highways. I think this is a fair compromise given that boundary names render along the boundaries at various zooms, making it still somewhat clear that a boundary runs along a road.
• Consider thinning the inner "glow" of protected_areas/nature_reserves/... at mid zooms (specifically z10 and maybe z11) to decrease visual noise.

[polarbearing]

In your examples, is the highway "glued" on the boundary, or is it mapped seperately?

[btwhite92]

In these examples, the boundaries are mapped separately from the road, since the road ROW is not part of the protected area. This is still an issue where boundaries are "glued" to a highway, or where a highway itself is used as part of the boundary relation.

[jeisenbe]

I've tried out this idea (rendering protected_area boundaries under roads) previously, see discussion in PR #3887, though I was not very satisfied by the results in testing.

At high zoom levels, where roads are quite wide, the protected_area rendering would be entirely covered by the road fill.

[jeisenbe]

New PR #4127 has now been updated to move the protected-area line rendering layer below roads, to fix this issue.

[matkoniecz]

Sounds like #1199