The primary high-capacity route of a railroad, characterized by heavy traffic, higher track speeds, and the most sophisticated signaling and infrastructure. Mainlines carry the bulk of a railroad's revenue ton-miles and receive priority in capital investment. They connect major terminals and industrial centers.
A secondary line that diverges from the mainline to serve agricultural, industrial, or rural areas with lower traffic density. Branch lines typically have lower speed limits, lighter rail, and less sophisticated signaling than mainlines. Many branch lines have been sold to short line railroads or abandoned as traffic declined.
A track parallel to and connected at both ends to the mainline, used for storing cars, allowing trains to pass each other, or serving customers. Passing sidings are a fundamental capacity tool on single-track mainlines. Customer sidings are used for loading and unloading.
The land corridor owned or controlled by a railroad on which its tracks, structures, and facilities are built. Right of way acquisition was historically one of the largest costs of railroad construction. Railroads actively manage ROW for encroachments, environmental compliance, and disposition of surplus land.
A safety system mandated by Congress after the 2008 Chatsworth collision that automatically enforces speed limits, prevents train-to-train collisions, and enforces temporary speed restrictions, overriding human error. PTC uses GPS, wireless communications, and digital track maps to monitor and control train movements in real time. All Class I railroads completed PTC implementation by the 2020 deadline.