Hi Bill (and other interested in automobile traffic):

I gathered some statistics from the 1% carload waybill study on passenger and freight automobile shipments into a post that you may find useful as you think about your auto car fleet. For those interested, the post can be found here:

http://cnwmodeling.blogspot.com/2013/10/commodity-flows-of-automobiles-and.html

Regards,

Charles Hostetler