Track maintenance typically includes which of the following?

Track maintenance is primarily focused on ensuring the structural integrity and functionality of the railway tracks themselves. This includes tasks such as repairing rails, which involves fixing or replacing sections that may be damaged or worn down. Maintenance of ties, which support the rails, is crucial as well, as degraded ties can lead to instability and safety issues. Additionally, adjusting ballast—the gravel or stone placed beneath and around the ties—ensures proper drainage and provides the necessary support for track alignment and stability.

While other options involve important aspects of railway operations, they do not pertain directly to the maintenance of the track infrastructure. Installing new rolling stock relates to the vehicles that run on the tracks, upgrading signal systems is focused on the technology that manages train movements, and enhancing passenger amenities improves the travel experience rather than the track itself. Thus, the correct answer emphasizes the essential work required to maintain and preserve the track structure for safe and efficient train operations.