After a catenary power outage with two trains stopped on the same track between interlockings, the following train may not start until the preceding train has been moving for how long?

• A. 15 seconds
• B. 60 seconds
• C. 30 seconds
• D. 2 minutes

Answer: (C)

After a catenary power outage, two trains stopped on the same track between interlockings must observe a short movement interval before the second train can start. The 30-second window gives enough time for the first train to actually begin moving and clear the immediate block, and for signaling and track circuits to register that movement as the line stabilizes after power returns. If the second train were allowed to start sooner, it could enter a block that hasn’t yet been safely vacated, or collide with a train that hasn’t fully moved away. A shorter interval risks insufficient clearance, while a much longer one unnecessarily delays movement. Thirty seconds is the safety-conscious, practical minimum that aligns with how block systems and re-energization procedures are intended to operate.