Look at the website, especially the FAQ which describes the coaches: "Why are different railroad coaches being used this season? What can we expect?
If you are a returning guest on THE POLAR EXPRESS™ Train Ride, you may notice that we are utilizing different railroad cars this season. These recently restored coaches seat 85 passengers in a 3 x 2 arrangement facing the center of the car, which helps create a more intimate theatrical environment and offers more options for parties with odd numbers. These cars also feature lower seat backs, which makes it much easier for children (and vertically challeneged adults) to see our wonderful entertainers.
Please note that seats in Chicago will all face towards the middle of the car to create better sightlines and a center stage area for our performers. Seats 41 – 50 will be considered front row if you prefer to sit closest to the action. Each coach on THE POLAR EXPRESS™ Train Ride at Chicago Union Station offers the same class of service and all guests enjoy the same quality experience."
https://www.chicagothepolarexpressride.com/faqs/