Last month’s collapse of the Skagit Bridge in Washington, United States, may have been caused by the driver of a truck carrying an oversized load moving to avoid an oncoming vehicle.
A preliminary report issued by the US National Transportation Safety Board (NTSB) said: “The driver of the oversize vehicle felt ‘crowded’ by the passing vehicle so he moved his vehicle to the right.”
The report continued: “…the top of the load collided with the overhead portal and multiple sway braces on the far right side of the truss structure”.
As well as interviewing the driver of the oversized load, believed to be a casing shed on its way to Alaska, NTSB investigators also interviewed the driver of the pilot car.
She told them that a vertical pole fixed to front of her car to warn of low clearances was 4.9m tall.
The report said the bridge’s clearance in the centre lane, where oversize loads are supposed to travel, was around 5.18m. In the far right lane, where the truss is lower, the clearance was 4.47m.
Three people had to be rescued from the Skagit River when two vehicles went down with the stricken bridge section (NCE 24 May).
Work on a $15M (£9.6M) temporary span is expected to finish this week.