Additional bus companies, listed as existing during additional years or decades, are mentioned in old City Directories, and in the WPA American Guide Series of state guidebooks.
Suburban and interurban bus companies listed in the Russell's Official National Motor Coach Guide, which was primarily a resource for intercity bus lines.
Yellow Bus Line (to Midland and Clare and Mt. Pleasant, until 1948)
SAGINAW
Carrollton-Zilwaukee Transit Line - existed in 1940's.
Saginaw Suburban Bus Lines - existed in 1950's.
Saginaw Valley Lines - suburban served Saginaw, Zilwaukee, Carrollton.
Stafford Motor - existed in 1930's.
Thumb Bus - existed in 1930's to 1940's.
Zilwaukee Bus Line - existed in 1930's to 1940's.
BAY CITY
Doran Motor Bus - existed in 1940's.
MIDLAND
Midland Clare & Mt. Pleasant Bus Line - served Mt. Pleasant, Clare, Midland, Bentley.