A September 2013 report from the Association of American Railroads (AAR) provides data on rail chemical transport costs (per ton mile). Using this data and data from the United States Department of Transportation, chemical transport costs for truck and barge can be estimated.
The AAR data indicates that, in 2011, rail revenue (costs to the customer) for chemical transport was approximately 6.1 cents per ton mile. Click here to go to the report with this data. Data from the DOT indicates that from 1990 to 2007 truck transport (all materials, not just chemicals) averaged approximately 5.6 more than rail transport (all materials). Click here to see this DOT data. Assuming that the same truck increase (5.6x) over rail (all materials) applies reasonably well to just chemical transport, then this suggests that truck chemical transport in 2011 was approximately 34.2 cents (5.6 times 6.1 cents) per ton mile. In the same manner, it can be shown that chemical transport on barges was approximately 4 cents per ton mile (in 2011).
If the data, assumptions, and computations are correct, then 2011 benchmark chemical transport costs are 6.1 cents per ton mile for rail; 4 cents per ton mile for barge; and 34.2 cents per ton mile for truck.
The AAR report also provides approximate 2012 total tonnage of chemicals and total revenues (costs to customers) for this transport using all transportation modes (truck; water; pipeline; air; and rail). The report also provides the approximate percentages of the total tonnage and revenues attributed to the 5 transportation modes. From this data and the per ton mile cost data shown above (assuming the 2011 costs are reasonably close to 2012 costs), an average length of transport trip for rail, truck, and barge can be computed. My computations, if correct, show that the average rail transport trip was about 865 miles; the average truck trip about 190 miles; and the average barge trip about 500 miles. These mileages might also be useful benchmarking data.