The Human Traffic series of investigations is unavailable until you complete mission 12 of Act II. Once you do, ten new investigation icons will appear on your map. Each one shows you the location of an auction bidder. You can't miss him when you get to his location, because your profiler will turn red. Hack his phone. This will reveal the location of that guy's briefcase on your map. You can use
to set a waypoint for it and go there immediately, or you can go there later. You can do other missions, side missions, collectibles, etc. in between, if you don't feel like going there at that moment (they are often on the other side of the map). You can also hack several bidders' phones before going to scan any of the briefcases.
When you get to the briefcase location, you'll have to do an intrusion. These are always very simple, quick intrusions - much easier than the other ones in the game. Once you've intruded, scan the briefcase.
After you've scanned ten briefcases, you'll get an objective to go to a specific location and do another intrusion. This will end in a "criminal convoy"-type chase, where you disable the target's vehicle and take him down while trying to not get killed by his police escort. The achievement unlocks after you take him down, even if the police are still chasing you.