It seems that most people who work on Sylt can't afford to live there and use the trains to travel to and from their homes on the mainland. Afternoon traffic is heavy enough to require several additional services between Westerland and Niebüll or Husum in the evening peak and it's still standing room only on most trains.
223.010 had already worked one afternoon train to Niebüll and was on its way back to Westerland as NOB81750 at 16:45 on 29 September 2015. The photo was taken near the east end of the Hindenburgdamm around 2km west of Klanxbüll.