I think maybe it has something to do with faces or facial recognition. The creature could have just been another human but the driver didn't see them that way. We already kill each other easily as it is so add that fear of the other and an invading force wouldn't have to do much to kill us off. The "alien" could have been left there and thinks they are seeing an alien as well.I honestly thank you for this explanation because this pretty much cleared up suspicions i had
Fastest available route seems the most out of place but I genuinely think that the moon's influence could have created a warped / mutated person given the manipulative motifs of the series.
If they can manipulate tapes and recordings anyway we should we even believe what we're seeing? There's no place in the world you don't see the moon at some point.
Thinking about it that way it's easy for it to be an abstract evil, rather than a physical presence.