When you see that it means people used either newton or the AHG (auto heartline generator) tools to shape and bank their tracks instead of doing it by hand in the NL editor. If you search the forums you should be able to find more info and where to download those programs if you want to check them out. Otherwise, if you're hand-building then longer segments are fine, I doubt even the best hand-builders out there can build with 1-2 meter segments and come out with something smooth.