Yes, thank you @granitschädel for your explanation! The “tunnel” used to be much longer. Now it's only about 40 meters. 
According to OSM Wiki, tunnels are structures at least 80 meters long or more that run underground. 
Here at the "Jakobstunnel" there are artificial retaining walls on both sides, so it is more of a bridge.
Thank you and sorry for my spartan English with a translation App.  ;o) 