4537 and 1371 leave the loop at Urban-Loritz-Platz to work to Hütteldorf. There are no timetabled workings that use this loop and I suspect this tram was turned back there to help regulate headways following a disruption. Interestingly the advertising on this tram refers to "Die 49er Spur" at Westbahnstraße, but that is something I have only noticed subsequently and don't know if it relates to this route or is just coincidence.