Each player is trying to collect one passenger from each of four colors in his train car. One of each color passenger is waiting at each of four colored passenger stations. Each turn a player chooses a station to go to and pushes the train around the track to that station. Inside the engine is a pop-o-matic die that pops as you move the train. At the station, you may pick up a passenger that matches the color of the die if one is available and you do not already have a passenger of that color. A white spot allows you to choose any present passenger you do not already have and a black spot prevents you from taking any passenger. - BoardGameGeek