Except that the data from this study (from the 1950s) is talking about extrapolations from data, without actual real testing including factors such as aerodynamics. In the 1950's this was restricted mostly to planes.

Modern road cars are not aerodynamically neutral devices - the vast majority of them generate lift at speed*. I suppose that if we drove everywhere faster, the load on the roads would lower somewhat because the effective "weight" (viewed as the force of the car on the road) would be reduced.

*I know of a few which generate "downforce" but in general these are pretty exotic (usually race cars, or certainly sporty anyway).