In railway operations, what is a "signal"?

A signal in railway operations refers to visual or audible indicators that convey essential information to train operators regarding track conditions or train movements. These indicators are crucial for maintaining safety and efficient operations on the railway. They provide instructions that can include commands to stop, proceed, slow down, or change tracks, among other directives.

Signals are strategically placed along the track and use lights, flags, or sounds to communicate specific instructions to locomotive engineers. The proper interpretation and response to these signals are vital in preventing accidents and ensuring that trains operate safely and efficiently on the rail network.

The other choices describe different aspects of railway operations but do not capture the essence of what a signal is used for in this context.