The industry had long time experience with roller bearings applied to passenger cars, both heavy weight and light weight and steam locomotives. Great Northern, a paragon of thrift, started installing roller bearings on its 1937 Empire Builder and even started adding them to steam locomotives by 1940. I wonder how much unit prices fell so that GN added them to its express boxcars? GN waited until 1948 before ordering those newfangled all steel boxcars.
