I think so much focus is being put on this is the location of the abandonment and not just the abandonment itself. Why not a gas station, shopping mall, side street or deserted lot? This together with the scents being tracked leads me to believe it was left by AM and JR because it's such a peculiar ending. It doesn't seem purposeful but more like the result of get the **** out now and run, like no other option.
Idk, i was think stores and gas stations have cámaras and a freeway doesn't and people pay less attention on the side since they're focus driving.
About them running ... it would make more sense to continue driving with a full tank to a safe location other than the middle of freeway with nothing around.