What Are Those Little Blue Lights and Flags?

Question:  What are the little blue lights for that are placed on the rails in a yard? 

Answer:  Blue lights (for night) and other blue markers such as flags (for day), are an extremely important feature of modern rail safety.  The “Blue Flag” or “Blue Signal” system allows mechanical employees to work safely on, between, or under engines and cars.  No movement of engines or cars is permitted on any track under blue flag protection. 

Tracks that are blue flag protected have switches lined away from the track being protected and these switches have blue padlocks placed on them so they cannot be lined to the protected track.  If access to the protected track cannot be restricted by aligning switches, blue portable locking derail devices must be installed to prevent an engine or railcar from entering the protected track.  

Engines sitting on blue flag protected track have blue flags or lights placed directly onto their control stands or consoles.  Only mechanical department employees may place and remove blue flag protection (including the locks, flags and little lights).  Only mechanical department employees have keys for the blue locks.

You’ll typically see blue flag protection placed on arrival tracks after a train has arrived and the power is cut off and sent to the engine shop for servicing.  So, switches on either end lined away from the protected track and locked, and blue markers placed on the track at each end of the protected area.  This protects car inspectors as they perform car-by-car visual inspection of the newly arrived train (when they will mark bad order cars to be sent to the car shop for repair). 

You’ll see blue flag protection used in car repair and engine servicing areas as well.

Finally, you’ll see blue flag protection in place on departure tracks to protect mechanical employees as they inspect outbound trains and perform the required air brake system tests.  Once the mechanical department has done their thing, they will remove the blue signals, then let the yardmaster know the train is released and ready to prepare for departure.

Thanks for asking.  Stay safe out there.  Here we go!