Authorities say drivers in St. Clair and Bibb counties were stopped at roadblocks in the area and were asked to give DNA and blood samples as part of a study.
Officials say giving samples was voluntary and participants were paid $10 for mouth swabs and $50 for blood samples.
St. Clair County Sheriff's Lt. Freddie Turrentine tells The Birmingham News authorities were helping with a study by the Pacific Institute for Research and Evaluation in partnership with the National Highway Safety Administration.
Authorities say off-duty deputies and fire officials stopped cars in Pell City and throughout Bibb County Friday and Saturday.
Turrentine says the samples were anonymous, and the study was aimed at finding out how many people were driving with alcohol or prescription drugs in their systems.