|| Due to the number of persons with commercial drivers licenses, much of Halliburton's workforce falls under Dept. of Transportation regulation. These employees are tested much more frequently than those who are not required to hold a CDL. Being in the energy(oil and gas production) buisness it is subject to frequent and widespread layoffs. In order to lose as many employees without paying severence pay and unemployment benefits, Halliburton will sweep entire departments with drug screening before layoffs begin.