Just north of the intersection of I-94/39/90, where 94 splits off to go to Milwaukee and turns into WI-30, at exit 138, there is a U-turn that leads into a maintenance building. Around the U-turn is a series of screens along a fence. One or two Wisconsin state patrol cars will sit in this U-turn and try to catch speeders from either direction. This is a highly popular speed trap, I almost always see a cop in this location.