Our friends over at Forgotten NY recently published this interesting pic of the 11-Train, a line which does not exist, but was once a proposed line number for the 7’s express route.
Notice that the color of the bullet is purple, the same color as the Flushing Line, or #7 train. At one time there was a proposal to give the express run of the #7 train a different number, and 11 was selected. Other IRT express runs were to be given Numbers 10, 12 and 13. None of these renumberings ever went through, but they were put on the roll signs just in case they ever were.
via Forgotten NY