Urea Ammonium Nitrate Solution (UAN) is a colorless liquid with a slight ammonia odor that is produced by combining urea, nitric acid, and ammonia into a liquid solution. Farmers prefer UAN because it can be applied more uniformly than non-liquid forms of fertilizers.

In the United States, UAN is transported via rail, truck, and barge. It is typically a splash loading operation when loaded into trucks or railcars via loading arms. UAN itself does not pose an inhalation hazard. However, decomposition of UAN may produce nitrogen oxide and ammonia vapor, so operator diligence of vapors must be observed. Vapor recovery, while not required, should be considered while operators are on top of the vehicles during the loading process to further increase the level of safety during the loading/unloading process. 

UAN is typically transported in 20,500-gallon tank cars. The rails cars themselves are 9′ outside diameter with an overall length of ~47′, with offset crashbox openings of varying length and widths.