on a block of downtown san francisco, there are two block-long lines labelled 'address interpolation'. there aren't many nodes along this block, but the ones that exist mostly have explicit addresses assigned.
these were created 14 years ago (potlatch 0.10f). what do they do, are they valuable to renderers or to the map itself?
I don't know how it renders, but the idea was you could mark the address at the beginning of the block and the address at the end of the block, and then address finders would try to guess the intermediate addresses if anybody asked for them.
I think they've fallen out of favor and now people just add addresses to every building. Maybe.
It's documented in the wiki: https://wiki.openstreetmap.org/wiki/Addresses#Interpolation
It was very useful in the early days, when no housenumbers were mapped, to fill the map quickly. If all numbers mapped since, you can delete this line.
Search and navigation software supports these elements. I just checked, osmand interpolates the location of a number if you search for it. Nominatim and OrganicMaps both just find this line if you search for an intermediate number.
As others have said, these are lines to make it possible to guess where a specific house number might be based on the start and end numbers of the line.
I usually recommend against deleting this kind of thing unless you can confirm that locals don't care or if it's not present in surrounding blocks.
