How does the FRA limit superelevation?

The correct answer is based on the fact that the Federal Railroad Administration (FRA) establishes height standards for superelevation to ensure safety and performance on curved tracks. Superelevation refers to the banking of a track at a curve, which helps counterbalance the centrifugal force acting on a train as it navigates that curve. By defining height standards, the FRA effectively limits how much a track can be elevated to maintain safe operating conditions for trains traveling at various speeds.

Setting specific height standards ensures that the superelevation is neither too low nor too high, which could lead to instability, derailments, or excessive wear on the train and track infrastructure. This regulatory approach helps maintain a balance between operational efficiency and safety, ensuring that trains can navigate curves without unnecessary risk.

The other options relate to aspects of train operation and track management, but they do not directly address the established regulations regarding the physical dimension of superelevation itself. By focusing on height standards, the FRA prioritizes a uniform and regulated approach to managing curves on the rail network.