I 1925 hadde Hertz styreverv og ledende stillinger i blant annet disse foretak President of the Yellow Cab Company Chairman Benzoline Motor Fuel Company Chairman Chicago Motor Coach Company Chairman Fifth Avenue Coach Company Chairman New York Transportation Company Chairman Omnibus Corporation of America Chairman Yellow Coach Manufacturing Company Chairman Yellow Sleeve-Valve Engine Works Chairman Yellow Truck and Coach Manufacturing Company I 1926, solgte han aksjemajoriteten i Yellow Cab Manufacturing Company sammen med datterselskapene, Yellow Coach Manufacturing Company og «Hertz Drive-Ur-Self» til General Motors. Hertz ble styremedlem ved GM samme tid.