
The first car behind the engine is the wheelchair car. In place of the row of seats that faces front, there is an empty space that wheelchairs can park in.
Many people don't realize that there is a ramp to get up to the Main Street Station. It is on the side closest to the City Hall.
Looking at this map, go straight down (toward the train) from the "M" in Main Street USA. The ramp is fairly steep and has a couple of switchbacks, but it gets you up to the wheelchair boarding area.
You can also choose to fold the rental wheelchairs and hold them on the train seats if you choose. But, you will still need to use the ramp to get up to the Main Street Station.
The Toontown Station is the easiest, there is a not very steep ramp to get on and off the train.