The word highway in the sense OSM uses it predates cars and means pretty much any path. Think of highwaymen, for example. See https://www.law.cornell.edu/cfr/t

The word highway in the sense OSM uses it predates cars and means pretty much any path. Think of highwaymen, for example. See https://www.law.cornell.edu/cfr/text/23/924.3 https://www.law.cornell.edu/cfr/text/23/924.3 which includes public pedestrian paths.