The Südbahn climbs up the valley of the River Riß, a tributary of the Danube, from the Ulm area to a point between the closed stations of Essendorf and Wattenweiler. It then drops into the valley of the Schussen, which it follows all the way to Friedrichshafen on the Bodensee.
218.464 and 218.434 had just crossed the watershed with IC119 and were speeding downhill towards their next stop at Aulendorf on 23 September 2013.