What actions must be taken prior to a track car receiving Rule 280a signal?

The requirement for verification that the track is clear before a track car receives a Rule 280a signal is crucial for maintaining safety operations on the railway. Rule 280a signals pertain to scenarios where a track car is being authorized to occupy a specific section of track, and ensuring that the track is clear of any obstacles or other trains is a fundamental safety measure. This verification process helps prevent accidents and ensures that the area is safe for the track car to operate.

The other options, while related to railway operations, do not specifically address the critical necessity of confirming a clear track prior to the issuance of the Rule 280a signal. Signal confirmation from the RWIC, the presence of additional equipment, and sending a clearance message to the engineer are important aspects of communication and operational protocol but do not take precedence over the immediate need to ascertain that the track is free of obstructions or hazards. Thus, verifying that the track is clear is the most important action to be taken.