The common 1/64th scale automobile and trucks must lead the people at Lionel and MTH to offer 1/64th scale Auto Carriers and Intermodal Flat Cars from the 1960's to the present.
The 89' Auto Carriers can be filled with 1/64th scale automobiles that are less expensive than in other scale.
The common place 1/64th scale Highway Tractor & Trailer sets from ERTL and others would surely lead Lionel and MTH to produce 89' Flat Cars and 3-Unit Spine Flat Cars in S Scale.
Andrew