The fasted cars crashed into the slower ones in front. Sending some moderately fast or quite slow cars would result in a big queue of unhappy customers. So basically, sending all cars with the same speed looks fine enough regardless of what the customers prefer. That is how it really works. We can prefer anything we would like when visit the Roll Coaster, but it would not matter for the machines, lol.
Additionally, the graphics (epsecially UI) are the best part! 2D sprite layers really does feel like a pseudo-3D. Neat!