As you enter into Shelby County west bound on I-40 around mile marker 35 the speed limit drops from 65 to 60 miles per hour (55 for trucks). It is clearly marked but is heavily partroled between the Shelby County line and mile marker 20 primarily for west bound traffic but they do have to turn around to go back to the county line after writing tickets. There are 2 full-tme dedicated unmarked white Ford Expeditions assined to this area along with several other unmarked cars routinly prowling. I travel this stretch daily and invaribly I see at least 2-4 cars pulled every day particularily around exit 24/25 at the 385 intersection. While it may not technicaly be a speed trap as it is marked it is a major revenue enhancer for Memphis/Shelby County enough so that they dedicate 2 full-time vehicles 24/7 at the county line.