marker light

plural marker lights

1. rail transportA light marking the end of a train.

   1 more example

   No sooner had a waiting locomotive backed on to its train, the vociferous 4-6-4 or 4-8-4 re-emerged from under the bridge, and the two red marker lights on the last vehicles passed, than the headlight of the electric engine hauling the following train could be seen under the bridge and the waiting queue of locomotives had moved up one.

   1954 January, H. P. White, “Vignettes of the Rail”, in Railway Magazine, page 54, at Harmon station, New York