What type of devices might be used in a Train Approach Warning System?

The correct answer, which involves the use of visual displays and audible alarms, reflects a comprehensive approach to ensuring the safety of roadway workers near train tracks. A Train Approach Warning System is designed to alert workers to the impending approach of a train, and utilizing both visual and audible signals enhances the effectiveness of warnings.

Visual displays, such as flashing lights or signs, are crucial because they can catch the attention of the workers who may be looking away from the tracks or engaged in tasks that require concentration. Audible alarms provide additional sensory input, helping to ensure that the warning reaches workers even if they are not looking toward the source of danger. This dual-system approach takes into account different conditions that may affect a worker’s ability to perceive a warning, such as distance from the tracks, background noise, or visibility due to weather conditions.

The other choices do not provide the same level of safety. Only using audible alarms could be ineffective in noisy environments where workers may not hear them. Solely visual displays might fail if a worker's line of sight is obstructed or if they are not focused in that direction. Manual flagging devices do not serve the same purpose as a warning system designed for approaching trains and rely heavily on the constant attention and presence of a flagger,