In an effort to perserve lamp life, most railroads keep their signals unlit when there are no trains occupying the immediate or adjacent blocks, but this economy and efficiency is not completly observed.
A case in point is a signal post on a single track along the ex-LV nee Conrail line in Central New Jersey. The post has two heads controlling e/b traffic and guards a switch just before the line becomes double track about 100 feet further east.
As e/b traffic approaches, the heads become lit about five minutes before the train approaches. As the train passes, the signals change to red over red, as expected. About 100 feet after the last car passes the post, the heads become dark once more.
W/b is a little different. As a train approaches, the heads remain dark. When the lead locomotive passes the post, the heads energize and show red over red. The signal remains at that aspect until the w/b clears the block, then goes dark again.
Recall this is a single line section of track. I would expect there are as many e/b movements as there are w/b. For those lamps to be lit for w/b trains seems to be needless and a waste of lamp life.
Undoubtedly, the heads are lit w/b only because there is no detection mechanism to distinguish which way a train is moving through the block. Installing whatever it would take to sense that direction probably would be far more costly than the expense of changing lamps more frequently.
Or is there more to this story than that?
RJ Emery near Santa Fe, NM
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