Hi James
You can just merge them together using the "Merge Route" option on the main menu in Surveyor. All of them are set at round about 0 height so the merge is quite straight forward. Just remember to leave space for an extra board or two between each module so that you can add scenery to blend the change over better. The military module doesn't interest me but I've added that route to the others and replaced the military part of it with a power station. Even without the military stuff it is still a really nice section to add to any US route.
Regards
Brian