Hammersmith Flyover is an elevated roadway in west London which carries the A4 arterial road over and to one side of the central Hammersmith gyratory system, and it links together the Cromwell Road extension (Talgarth Road) with the start of the Great West Road.
Completed in 1962, it was one of the first examples of an elevated road employing reinforced concrete balanced cantilever beam supports with a single central column. The deck spine and wings are of hollow prestressed concrete design, with each span being tensioned by longitudinal tendons (four clusters, each of sixteen 29mm steel cables)[1]. The flyover was designed by G. Maunsell & Partners, Consulting Engineers, led by Peter Wroth.[2]
Marples, Ridgway and Partners, a Westminster-based civil engineering contractor, built the flyover at a cost of £1.3 million. The then Conservative Transport Minister Ernest Marples had been a Marples, Ridgway shareholder. To avoid a conflict of interest Marples undertook to sell his controlling shareholder interest in the company as soon as he became Minister of Transport in October 1959, although there was a purchaser's requirement that he buy back the shares after he ceased to hold office, at the price paid, should the purchaser so require.[3]
The flyover was closed on the 23rd December 2011 after structural defects were discovered, Transport for London estimated that repairs would last until at least January 2012.[4][5] The Fulham and Hammersmith Chronicle and other media organisations claim that they were contacted on the 14th December by a whistleblower who revealed that problems with the structure were far more severe than was being made public[6][7].