A train standing on the main track to meet an opposing train in ABS must not line the switch until which event occurs?

• A. The opposing train has entered the block in advance
• B. The opposing train has left the block
• C. The dispatcher issues a direct order
• D. The signal indicates proceed.

Answer: (A)

In ABS, you only line the switch for a meeting after you know the opposing train is already in the block that lies in front of the switch. That occupancy confirms a protected route: the opposing train is in the block ahead, so routing the meet won’t place either train into an unsafe or conflicting path.

If the opposing train hasn’t entered that block yet, lining the switch could create a misrouting or a collision risk. Waiting for the opposing train to enter the block in advance ensures proper protection. Dispatcher orders or a proceed signal don’t substitute for this occupancy-based safety requirement in ABS.