I think they are clones that are all symbolically linked to one proto-consciousness. All the green ones are the same soul, same with the red, brown, yellow et al. They all exhibit the same personality trait and plus, they seem to bang each other, which would be weird if they were all the same individual.
I did the San Francisco to Denver portion when I was a kid and had such great memories that I reasoned taking a college spring break trip from Boston to Florida would be just as good! And I was right! Only by ‘good’ I mean ‘terrible’. You should also keep in mind that the people who do long distance train travel are sometimes there because they’re not allowed to fly on planes anymore.