The D XI, also known by its later designation PtL 3/4, was the most numerous of the Bavarian local railway locomotives. It was designed and built simultaneously by Krauss and Maffei and procured over a period of 19 years. Externally, they were very similar to the D VIII, which had been in production for a number of years, but they were intended more for routes on flat land and were therefore somewhat lighter and weaker. On the other hand, the coal reserves were larger, since the greater weight on the trailing axle, which was placed far to the rear, had less of a negative effect on the driving characteristics on flat land than on inclines.
Due to the long distance of the trailing axle, this was linked by a Krauss-Helmholtz bogie, as had already been used on the D VIII. The brakes on the locomotive were also state-of-the-art, and despite the changed area of operation, a Riggenbach counter-pressure brake was used in addition to the counterweight brake and the modern Westinghouse air brake.
In addition to the state railway, the LAG also bought eight engines from Krauss, which were later bought up by the state railway. There were also three examples that came to the state railways from the Murnau–Kohlgrub–Oberammergau light railway via the LAG. Thus the total number of D XI or PtL 3/4 reached 147 copies until 1914. A model derived from them was the Palatinate T 4II, which was only built three times and had slightly different dimensions. After the war, all engines came to the Reichsbahn and became the class 984-5. About half were retired in the early 1930s. After a few losses in World War II, the Bundesbahn took over 56 units, the last of which was in use until 1960.