River Class Vessels

I am doing research on River Class Vessels and wanted to know the specifics of the class as well as the advantages/disadvantages

Here’s what I understand so far:
[li]~650 ft in length[/li][li]~72 ft beam[/li][li]15K-20K ton carrying capacity[/li][/ul]

Here are my questions:
[li]What percentage of total cargo does River Class haul on the Great Lakes?[/li][li]Is this cargo amount growing or shrinking over time?[/li][li]What is the advantage of River Class vs. other classes?[/li][li]What ports are used most by River Class?[/li][/ul]

Any help would be appreciated. Thank you.