Even good ol' Henry Ford had fantasies about could-be Detroit public transit systems.
According to Detroitography.com, Ford had concocted an 81-mile rapid transit plan but recognized that feasibility and funding weren't there.
Detroitography also indicated that the main lines important for Ford were:
Grand River-Schoolcraft Line
“[...] conveniently located for the low-income low-auto-ownership residents of the area. Six more stations serve an [extensive[ residential corridor of about eight miles lying directly north of the site. In a second phase, the line would continue to Merriman Road [...]“
“[...] this line on the system originates in the Central Business District running in subway under Michigan Avenue to the Lodge Freeway and sharing some stations with the Grand River-Schoolcraft line in the CBD. [...] In a second phase, the Michigan-Airport line continues along the Penn Central right-of-way, wit stations in West Dearborn and Inkster.”