An important part of contemporary US railroading is short lines. A Short Line (for example, the Aberdeen, Carolina, and Western RR) is a smaller rail line that serves customers along its tracks. Sometimes, short lines sadly loose their main customers and are shut down. Occasionally, these short lines (such as the Nevada Northern RR) have been converted to museum lines. The other cool feature of short lines is that they often run interesting older diesel locomotives (ie: Alcos, FMs, early GEs, Baldwins, or classic EMDs), and some short lines even have operational steam locos, like the WM Scenic RR with their 2-6-6-2 #1309. Some short lines run excursion passenger services (the AC&W and WMRR both have passenger trains too). An interchange is where two railroads exchange freight cars with each other. Many short line railroads have interchanges with Class 1s. Even the Class 1 RRs interchange cars with each other. I've mentioned a few well-known US short lines in this post. I'd love to hear some of your ideas. Post them in the comments.
We'll likely never see class 2 or 3 railroads in TSW. They simply just don't run enough trains to fill up a timetable. Wouldn't sell, therefore not worth putting in the effort to make it
Most of the substantial shortlines are umbrella owned by a handful of companies that won't give rights to DTG. An example is the Genesee and Wyoming which has well over 120 different shortline railroads but doesn't want to play ball. It is what it is. Also, the majority of the playerbase likes passenger routes, so anything that's not ALSO involving passenger operations leaves money on the table so there's very little chance of it being made. If however, you have a SPECIFIC short line in mind and it's not JUST freight, and you think DTG MIGHT be able to get a deal with them... then suggest it.