Some drivers along a busy Fort Worth street on Friday were stopped at police roadblock and directed into a parking lot, where they were asked by federal contractors for samples of their breath, saliva and even blood. It was part of a government research study aimed at determining the number of drunken or drug-impaired drivers. NBC DFW confirmed that the survey was done by a government contractor, the Pacific Institute for Research and Evaluation, which is based in Calverton, Md.