This applies to Chicago’s mass transit system. (The metra has a different system)
Front and back car:
not in a rush, easy going
Middle car (where most CTA exit stairways are):
In a rush. Packed. On a mission–wanting to be the first up the stairs to exit the station. Or could be the tourist, because they don’t meander far from the stairs when waiting for the train. The mix between the anxious and the tourist is a deadly mix.
Car behind the leader, or car in front of trailer:
the compromiser

Later at night, it seems ladies ride more in the middle cars for safety.
During rush hour, i’m a front car rider. Later at night, I like to ride the middle cars, because they are more entertaining.
Because the exit at the chicago stations for the Metra is at the front of the car, their system is fairly linear. Front car riders are the more anxious pushy crowd. With it getting more laid back the further down the train you go.
I tend to be in one of the front cars on the way to work (going south) and in one of the back cars on the way home (going north). These cars are less crowded and I have a better chance of getting a seat.
i think “late at night” spudart is in the middle cars for the ladies. just when you ladies thought it was safer there!
i ride the back car of the green line, because it’s closest to the exit at the station i get off at.
I don’t ride the trains a lot anymore, especially since downtown has become my “bubble” and is so walkable. I used to be a last car rider, for any number of reasons, but once the system genuinely improved in the mid-to-late 90’s, it was because the last car was usually the least crowded. If I take the train now it’s usually to and from O’hare and I try to sit in the first or second car because they are closer to the exit. Matt is right about middle car riders, and I avoid them as much as possible.
wow. back in march i used to ride the green line. what a bear that was, going all the way out to the west side to work. glad that’s over! what about “what kind of bus rider are you”? i like to ride near the front of the bus at night, so the bus driver will protect me [in theory”> from crazies. but during the day, i like to ride in the back. it’s a whole other world back there. especially in those really long two-part buses.