This is a beautiful map even if it represents the plans that have doomed most of our country’s major cities to car-centric planning. The map is part of the UM Clark Library map collection. In 1925, “super highways” were simply 204 foot wide major surface roadways. Notably, those super highways were absent from the city’s core and center.
DETROITography 
Right of Way reservation/preservation was becoming a major initiative in the 1920s. It was expanded through legislative efforts.
http://legislature.mi.gov/doc.aspx?mcl-act-381-of-1925