In a follow up to my musing in the Carthage Marble post about researching commodity flows, I came across a modern-day data set called the Public Use Waybill Sample provided by the STB. The data files themselves are large and in record format that can be deciphered using this guide. I'll play around with one to see what it might provide. Microsoft Excel should prove handy for splitting the data file into usable fields.
Parsing this data with the MSExcel Text Import Wizard is quite error prone, but it worked for a quick test. The file is longer than my outdated version of Excel can handle (>65535 rows). For the previously posed question about cut stone products, there is an Standard Commodity Code (STCC) series for it (328**), but in what I managed to open of the 2011 sample, there was only a single 32819 Clay Stone Products shipped in a trailer on a single unit flat car.