That's a heck of an interesting chart!
1579+ thousand cars in service in 2007 vs 1669+ thousand cars in service in 2019 would signal an increase in in traffic, but i think that is misleading as the two varieties of cars that have gone up is covered hoppers and tank cars. These two types are most likely to be empty one way, where as boxcars and gondolas can be loaded for each trip. Boxcars and Equipped boxcars are both significantly down percentage wise, and I can only see the need for open top hoppers to continue to decline as environmental pressure and other factors push down the need for coal.
Thank you for posting this.