In OSM, "highway" means "any road, street or path" - the meaning is specified by highway=motorway, or highway=-residential, or even highway=footway. Construction is designated by highway=construction , with construction=* `construction=` specifying the *type* of construction. "construction=highway" does *not* add any extra info on *what* is being constructed; "construction=motorway" does. I think you might be confused by the "motorway" meaning of the *word* "highway" - in OSM, `highway` is a keyword, not a road type.

In OSM, "highway" means "any road, street or path" - the meaning is specified by highway=motorway, or highway=-residential, or even highway=footway. Construction is designated by highway=construction , with construction=* specifying the *type* of construction. "construction=highway" does *not* add any extra info on *what* is being constructed; "construction=motorway" does. I think you might be confused by the "motorway" meaning of the *word* "highway" - in OSM, `highway` is a keyword, not a road type.