In response to questions raised by the petrochemical industry, the federal Department of Transportation (USDOT) amended its emergency order restricting those who transport crude oil by rail in the United States last Thursday.  Among other revisions, the amended order requires that shippers test their oil cargoes with sufficient frequency to ensure that their hazardous material classifications remain accurate and current.  The amended order also gives some guidance as to accounting for the variability of the material, including the time, temperature, and location of its extraction.