Sentence:  [...] unlike the latest British yards, Gremberg has only primary <WSD>retarders</WSD>, manually operated, a method that the hump operators apparently prefer to electro-pneumatic control because they can grade the braking pressure more accurately by feel. 
Meaning of the word marked with <WSD> tags:  (Q1779780)  A device for slowing down large trucks, lorries, buses, shunted railway wagons.