Here in southern Michigan, the Amtrak line runs parallel to I-94. 94 is just two lanes in each direction and semis account for over 25%. It's a dangerous traffic situation, and that doesn't account for smuggled drugs, tainted poultry and produce that the motor carrier patrols find on a regular basis.
I'd love to see fewer trucks and more railway cars, but it boils down to NIMBY. There was a plan to create a large depot in the Detroit area where trucks could pick up shipments from railway freight for local delivery, but that was trashed when residents thought it would be too noisy.