A westbound Conrail freight is being pushed upgrade just west of Horseshoe Curve in 1989. The rear unit has its classification/marker lights illuminated red. If a locomotive is on the front of a train, the lights can be either white (unscheduled train) or green (meaning there will be a following section of the same scheduled train that day). In these cases, the lights are "classification" lights. On the rear, however, they can be red, which would make them "marker" (rear end) lights.