Please anybody have any suggestions of how to simplify this volume?

I am trying to simplify this train volume from sketchup warehouse. I’ve tried surface network but I cant get it to work. I dont understand why. I studied dave schulz method on lynda but his objects hare more loose. I still want the streamlined look.

metro_help.3dm (717.1 KB)

Use multiple surfaces. Create each large surface as a separate Rhino surface, and then use chamfers, fillets or blends at the corners between the surfaces.