What is the function of the predictor circuitry at a level crossing?

The function of the predictor circuitry at a level crossing is to calculate the time until rail traffic reaches the crossing. This is crucial for ensuring the safety of both trains and vehicles at the crossing. By accurately measuring the distance and speed of the approaching train, the circuitry can determine how much time is left before the train arrives. This information is used to anticipate when to activate signals, alarms, or gates to warn or protect road users, allowing for adequate warning before a train crosses the road. This predictive capability helps prevent accidents and maintain safety standards at level crossings.

The other options relate to different aspects of level crossing operations but do not accurately describe the primary function of the predictor circuitry. For example, while alerting train crews or signaling speeds is important, those functions are typically managed by other systems. Opening gates automatically is also a function related to level crossings but is controlled by the timing and data processed by the predictor circuitry rather than being the main function of the circuitry itself.