Code of Federal Regulations Title 5. Administrative Personnel § 5.930.108 Periodic medical evaluation

At least once every 4 years, each agency will ensure that employees who operate Government-owned or leased vehicles are medically able to do so without undue risk to themselves or others. When there is a question about an employee's ability to operate a motor vehicle safely, the employee may be referred for a medical examination in accordance with the provisions of part 339 of this chapter.