The Illinois State Police utilizes hand-held radar, moving radar, pacing, laser speed measurement devices and air speed measurement to determine the speed of vehicles. The first mechanical means to measure vehicle speed was the stop watch. As early as 1906 the courts accepted that the time it took a vehicle to travel between two points could be converted to vehicle speed. Using the speedometer and keeping pace with another vehicle has been utilized since 1916. The Illinois State Police started using radar in 1956.
Radar uses radio waves that bounce off moving vehicles.
In 1959 the state police started using the stop watch method of measuring vehicle speeds from airplanes. The state police now operate a fleet of fixed-wing aircraft for speed enforcement. In the 1970's, hand-held radar was made available to most troopers. In the 1980's, moving radar enabled troopers to clock the speed of vehicles approaching from the front or rear while driving down the highway. In the 1990's, laser speed measuring devices were introduced.