["Sedan"] = new TrainCarPrefab("Sedan", "assets/content/vehicles/sedan_a/sedanrail.entity.prefab"),

How does the sedan rail make sense for this plugin? It has no coupling points so it can't attach to other train cars. Does it have a parent trigger so players can ride on top, or can players mount the other seats?

Hmm, I wonder if I could add invisible coupling points...

Yes, players mount the other seats.