Rheinische Esel is the name of the railway line opened in 1880 between Dortmund-Löttringhausen and Bochum-Langendreer. It was built with extremely low gradients in the northern foothills of the Ardey Mountains and runs partly on high embankments over the area. From Löttringhausen with a connection to the Dortmund-Hagen railway line, the route first heads west past Kruckel and Annen to the Witten-Ost freight yard. Here the course changes in a northerly direction past Stockum to Langendreer with a connection to the railway lines from Dortmund to Bochum and from Hagen to Bochum, which still separate there today. For the most part, today's S-Bahn route from Dortmund to Witten follows the Rhenish donkey at a surprisingly short distance. The length of the route was about 13 kilometers. The main users were the freight traffic of the adjacent companies and mines and the workers who used the train on the way to work there.