What does unbalance measure in railroads?

Unbalance in railroads specifically refers to the force required to offset superelevation on curved tracks. When a train travels around a curve, the outer rail is typically elevated relative to the inner rail to counteract the lateral force experienced by the train due to centrifugal force. This elevation, known as superelevation, helps to keep the train balanced and stable on the curve.

Unbalance measures how much additional force is required for a train to remain stable, taking into account the degree of superelevation and the speed of the train. If the track is not properly balanced, it can lead to issues such as derailment or excessive wear on the rails. Therefore, understanding unbalance is crucial for maintaining safe and efficient operations on curved sections of railway.

While other options may relate to various aspects of rail operations, they do not specifically address the concept of unbalance as it pertains to the dynamics of superelevation and lateral forces in curved track scenarios.