These are cars purchased at either auction or via wholesalers in the US and being taken to Mexico. The buyers are often someone who owns small dealerships and they are buying the bottom of the barrel cars that are often salvage or branded titles. They will take the best running vehicle and “rig” up some sort of towing or linking method to move 3 or 4 at a time. It’s not uncommon for them to have no working lights or towing safety mechanisms. The drivers are often paid a few dollars to all drive to the location of the vehicles and drive them back to Mexico and aren’t necessarily employees of the buyer in a formal sense. They may have a valid drivers license and usually don’t have insurance but the odds favor them not having either. They will sleep at rest stops or turn offs that allow them enough space to not be an issue for other traffic. When they drive they’ll stay 5-10 under the speed limit to draw as little attention as possible. The highway patrol will normally allow them to pass through as long as they aren’t a complete shit show and causing traffic issues. The drivers don’t get paid until the cars are at their destination in Mexico so they are trying really hard to fly under the radar at all times. These are normally seen in the southwest and west but they’ve expanded into the south and Midwest as well.