southwestforests - our posts "crossed"!
Unlike Trainz, you cannot design and create stuff. Or modify things. The developers - 3DTS (who you may remember from MSTS days) have kept it that way so everything works - which it does.
Here is a link to their site...
Train Simulator World by Run 8 - We put the TRAIN back in Train Simulator
Unlike other sims, there are not a huge number of routes - SoCal and CSX West only, but given the realism factor, there are more than enough. With the base route (SoCal - Barstow and Needles) for example, you get 440 + miles to run - all prototypical.
For SoCal additional routes available are Cajon, Bakersfield, Seligman and San Bernadino. These can be run separately, but in actual fact, as you add them they all link to one another and become a continuous huge route (providing obviously they are geographically adjacent). And everything grows - so San Bernadino, for example, would add 330 + extra industries, with all the operational possibilities and so on.