|Link to The Londonist|
"Ever since work began on the Cromwell Road Extension in the 1940s, a complicated set of junctions at Hammersmith Broadway prevented the scheme from linking up with the Great Western Road. In 1962 the Hammersmith Flyover opened to much acclaim, providing this missing link. It is this structure whose current state of ill-health is bringing West London to a grinding halt. The source of its woes are the corroding steel reinforcement cables, but they are most certainly not to blame.
"The Hammersmith Flyover is an ingenious design. It was necessary to provide an elevated carriageway 61 feet wide in a space that was only 28 feet wide, using a construction site suspended above a busy arterial traffic route that was to remain operational."