I just found a good trick on the German site to create flatter landscapes. There is a texture file named ridge.tga that creates the hills on a map. Here is the path; Train Fever\res\textures\terrain\ridge.tga.
First backup the original then open this file in your graphics program, paint does not work, and change it to all black. Then save it, no compression.
When you create a new map it will be a lot flatter now.
note: if you make it all white, you will get large square ridges. Try it to see how this works.
This has been uploaded for those who don’t know how to change the color of this file. This is not my mod. This is made by the person who showed this trick.