Chemical shipments on U.S. railroads rose 4.4 percent last week, the Association of American Railroads said.

Chemicals shipments on trains, called rail car loadings, are a measure of demand for products ranging from plastics to fertilizers.

For the week that ended July 31, chemical rail car loadings rose to 29,083 from 27,848 in the year-ago period, the AAR said.

The figures often provide an early glimpse of broader trends for the chemical industry as well as manufacturing, according to analysts.

The weekly data indicated that year-to-date rail car chemical loadings have risen 11.6 percent, compared with the same period in 2009.

Rail car loadings represent about 21 percent of chemical volumes by tonnage. Trucks, barges and pipelines carry the rest. (Reuters)