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.
A siding long enough to hold an entire train, allowing a meet or pass between two trains on a single-track mainline. The length and spacing of passing sidings are key determinants of mainline capacity. Extending or adding passing sidings is a common capacity improvement investment.
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 short dead-end track branching off a mainline, branch line, or yard track to serve a specific industry or facility. Spurs do not have a runaround track and require the locomotive to push cars in and pull them back out. The term is often used interchangeably with industrial spur.
A railroad track owned or leased by a shipper or industry that connects their facility to the mainline or branch line, providing direct rail loading and unloading capability. Private sidings are the foundation of the carload business and give shippers dedicated rail access. Construction and maintenance of private sidings are typically the shipper's responsibility.
A track assembly consisting of a switch, frog, and closure rails that allows a train to move from one track to another. Turnouts are defined by their angle, expressed as a number (e.g., No. 10 or No. 20), with higher numbers indicating a more gradual diverging angle. They are a critical infrastructure component at every junction, siding, and yard entry.