During rush hours, the gets extended to Bedford Park Blvd. At the same time, the will run express in the peak direction.
As of the and , the and usually run normally, but during rush hours, the will run express in the peak direction. The trains also use the 239th Street Yard, so since it goes via the line to get there anyway, might as well run in service, so the runs to Nereid Avenue to enter the 239th Street Yard. The reason it doesn't run express on that stretch (I dunno why it doesn't run express at least between 180 and Gun Hill Rd, maybe it is due to the delay caused by the switches) is because Nereid Avenue is a local station, and even if there are switches from express to yard, it won't be able to enter the yard easily while providing as much service as possible.