That isn't actually clear. While trains claim they are the most efficient, they use measures like ton-mile that make them look much better. Trucks are often used for light things which means the ton-mile would go down. Trucks are often used for small loads, trains to all those different destinations with small loads would be less efficient. Sure steel wheels have less rolling resistance than rubber, but it isn't that much less. Long trains are more aerodynamic, but trucks already have a fair amount of length to spread that would over.

As such it isn't clear how much more efficient trains would be in the real world of freight.

Note that the above is about freight. Transporting humans as a number of different factors making the above inapplicable.