An investigation into how a five-by-four metre road sign fell and crushed a car on Melbourne’s Tullamarine freeway in January has found the sign was missing a steel plate and several safety checks had not been carried out.
A report into the incident cites "weaknesses in quality control" in the design and construction process.
The full report has not been released but VicRoads told Wide Format Online in a statement that the sign's fall was caused by "progressive fatigue crack" which was the result of a crucial part not being installed.
"CPB Contractors [part of CIMIC Group, formerly Leighton Holdings], who delivered the project, carried out the investigation which has been independently reviewed and verified. It found the sign failure was caused by a progressive fatigue crack due to the omission of a stiffener plate during the fabrication process."
A ‘stiffener plate’ is a steel plate inside the gantry designed to strengthen the connection of the sign structure to the gantry.
"The investigation considered the full design and construct process to understand how the stiffener plate omission occurred," said VicRoads. "It found weaknesses in quality control and that several required inspections were not carried out.
"VicRoads, Major Road Projects Victoria and Transurban have audited similar signs on the Managed Motorway network and are confident this is an isolated incident. There was no evidence of stress or deterioration on any signs audited.
"However, Transurban will strengthen top-mounted static signs delivered as part of the CityLink Tulla widening project to ensure the 100-year lifespan is met."
CPB Contractors is also working on Melbourne's West Gate Tunnel project, Sydney's WestConnex and major road projects in Queensland and Western Australia.
The driver of the car, Nella Lettieri, who was on her way to pick up her daughter from Essendon Airport, suffered neck and hand injuries and is said to be considering legal action.