Three experiments were conducted to evaluate the effectiveness of using drone (passive or unmanned) radar guns on vehicle speeds in construction zones. Experiment 1 was an exploratory study to find the immediate (less than an hour) effects of using one drone radar gun. Experiment 2 was conducted for a longer time period (a few hours) to evaluate the effects of using one drone radar gun. Experiment 3 evaluated the effects of using two drone radar guns and their lasting effects on vehicle speeds. Experiment 3 was divided into three one-hour time intervals. This method was used to determine the lasting effects of drone radar. Data analysis included the comparison of mean speeds, speed distributions, percent exceeding a given speed, and net speed reductions. The immediate effects of using one radar gun (Experiment 1) were 8-10 mph speed reductions; however, such reductions should not be considered typical effects of radar signal transmission because of the exploratory nature of Experiment 1. Experiment 2 showed that using a radar gun was not effective in reducing vehicle speeds when drivers knew it was drone radar. Experiment 3 indicated that the use of two radar guns increased the effectiveness of drone radars, since drivers were not sure whether the signals were from a police radar or drone radar. The two radar experiments reduced truck speeds by 3-6 mph and car speeds by 3 mph, and the radar effects did not diminish over time. In Experiments 1 and 3 the percentage of vehicles with excessive speeds inside the work zones decreased when radar signals were transmitted. Furthermore, the decreases in Experiment 3 were sustained over a period of time.