ABSTRACT
The case history concerns a mixture of design, information and manufacturing failures, with a number of contributing factors. The 40-foot-high Brent Cross flyover, intended to carry Hendon Way over the North Circular, was under construction, and a mobile crane was being used to erect a large Scotch Derrick crane for the main works contractors, the Cleveland Bridge and Engineering Company. The base of the tripod of the derrick was 20 foot high, and the mobile crane was being used to place the king post on top of the tripod. Because of the length of the king post and the height to which it had to be lifted, the mobile crane had been fitted with an extension jib. It had lifted the king post 2–3 inches from the ground, when it slewed about two feet to one side and collapsed on the passing coach. The accident was primarily due to the design of a hinged section of the jib.
