First off. This trap moves a couple of blocks each time between Ashland and Halsted on Archer ave. On police car will half hide behind a building or corner and use a gun to track your speed. Several other police cars wait around the corner to go after you. The tell tail sign of this trap before you get caught is the flashing blue lights. You can see them a few blocks away. I have seen this trap used 4 times this past summer in the same area.