On the high-speed track from Hannover to Würsburg are many long tunnels. In case of an emergency they are very difficult or even impossible to reach by the usual rescue teams. Therefore are six of these special train stationed along this line. Al these trains are in the same combination of loco's and wagons. Each train has on both ends an identical locomotive, here the 714-110.
In case of an emergency the resue teams (Fire - Paramedic - doctor etc) come aboard the train and drive to te place of the emergency.
More info on
https://de.wikipedia.org/wiki/Rettungszug_(Deutsche_Bahn_AG)