A car veered off the carriageway as it was travelling on the M6 northbound between junctions 26 and 27 at around 6.30am today (January 7).
The car then slammed into railings on the outer edge of the 87ft Gathurst Viaduct, leaving a large hole in the barrier.
Fortunately, the car bounced back into the carriageway and avoided hitting any other vehicles.
The driver, who was cut from the vehicle by firefighters from Wigan, was taken to hospital with a "minor head injury".
A spokesman for Lancashire Fire and Rescue Service said: "Those railings saved her life for sure. It's a long drop down into the valley and if she had gone through them there was only one outcome.
"The car was badly damaged but once we had made room for her to get out - including taking the roof off - she was able to walk, which was a huge relief.
"It was the only vehicle involved but the accident caused traffic pandemonium on the motorway."
The M6 northbound at junction 26 and the M58 at junction 6 was expected to remain closed for "most of the day" for repairs and resurfacing, North West Motorway Police said.
Severe delays were reported in the area, with motorists reaching maximum speeds of around 5mph, according to the AA.
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