What is used to store sand in the operational context?

In the operational context of train operations, the correct answer pertains to platform ends. The platform ends are specifically designed locations where sand can be stored and accessed easily for operational needs such as improving traction on the tracks. This is particularly vital in situations where the tracks are contaminated by ice, snow, or other materials, as sand provides the necessary grit to enhance traction for the trains.

Storing sand at the platform ends ensures that it is readily available for train operators during their pre-departure checks or in situations where immediate action is required to maintain safe operations. This is critical for ensuring the smooth and efficient running of services, especially during inclement weather conditions.

Although other storage options like bins could be used for various materials, platform ends are optimized strategically in train yards and stations to support operational efficiency directly related to train performance and safety.