Thought I'd share some of my work. The first two are from school.
Started this one today.
Any idea on how to get these in Trainz?
Don't think Sketchup is the best source for Trainz objects. Too many polys is one issue. Vetices not welded is another. Then I don't think there is an exporter to create the IM files needed for Trainz. Best go for a real 3d modeling program, GMax, Blender or if you can afford it, 3DSMax.
Nice effort by the way. From school? I hope that was a legitimate school project.