Scope: 75 trains; 900 bogies; The “D78” stock bogies had been running on the District Line since the late 1970’s and were prone to fatigue cracking and wheel unloading. This was due to the high torsional stiffness characteristics of the original bogie frame and the low tare weight of the car bodies. SSL worked with Adtranz who designed and manufactured the new replacement bogies. Benefits: improved vehicle safety and reliability, increased mean distance between failures and reduced track and bogie maintenance costs.