scarecrow
n.— «The NYPD is using unmanned police cars on major highways as a deterrent to speeders, the Daily News has learned. The vacant vehicles—derisively referred to as scarecrows by some cops—were blasted by the city’s police union chief as a “symptom of drastic short-staffing.”» —“ Brass grasp at straw” by William Sherman New York Daily News (New York City) Apr. 30, 2007. (source: Double-Tongued Dictionary)