From English - German Ding/FreeDict dictionary ver. 1.9-fd1:
derailing wagon /dɪɹˈeɪlɪŋ wˈaɡən/
[Br.] Versuchswagen zur Untersuchung der Entgleisungssicherheit / von Entgleisungsphänomenen
Synonym: derailing railcar
see: railway carriage, carriage, railway coach, coach, railroad car, railcar, car, railway carriages, carriages, railway coaches, coaches, railroad cars, railcars, cars, compartment coach, compartment car, flanger wagon, flanger car, flanger, instruction wagon, instruction railcar, exhibition coach, exhibition car, suburban carriage, suburban coach, suburban car, end coach, rear coach, end car, rear car, lowmac coach, dynamometer coach, dynamometer car, lighten a wagon