What is the function of 'event recorders' on trains?

Answer: B — To capture operational data for later analysis or investigation

The function of event recorders on trains is to capture operational data for later analysis or investigation. These devices are critical for ensuring safety and improving train operations. They record various parameters such as speed, brake application, throttle position, and other critical performance metrics during a train's journey. This data is invaluable in the aftermath of incidents, accidents, or even routine evaluations, as it provides a factual account of the train's operations leading up to an event. Analyzing this data can help track down malfunctions, assess compliance with operating standards, and identify areas for improvement in both safety and efficiency. Other options, while related to train operation, focus on specific areas that event recorders are not designed to cover.