A woman whose car was crushed by a giant sign that fell from a Melbourne freeway gantry says she is lucky to be alive and wants answers from authorities.

Nella Lettieri, 53, escaped serious injury when the four-metre by five-metre sign fell onto her vehicle on the Tullamarine freeway, near Essendon Airport, about 5.30pm on Tuesday.

The mother-of-three was heading to collect her daughter when the near miss occurred.

Ms Lettieri is yet to decide whether to pursue legal action but said she wants answers.

“How did that happen? How did that happen here in Australia?” she asked during an interview with Network Ten on Thursday.

She initially thought she had hit another vehicle.

“It was like a roller door coming down right in front of you,” Ms Lettieri said.

“Had I been in my daughter’s car which is a smaller car, there’s no way I would have survived.”

Dashcam footage from a vehicle behind shows the force of the giant sign, moving Ms Lettieri’s car even though she had slammed on her brakes.

“I’ve hit the brakes and then I’m thinking ‘okay, I’ve hit the brakes why isn’t it stopping?’,” she said.

“It just kept pounding on the car and I thought ‘okay is it going to stop?’.”

The weight of the sign crushed Ms Lettieri’s car, shattering the windscreen and scattering glass across the highway. No other cars were hit.

Ms Lettieri was taken to Royal Melbourne Hospital with an injured arm and has since been discharged.

Daughter Stephanie said the family were expecting Ms Lettieri’s injuries to be worse.

“I was just shocked, I couldn’t believe she got out of that,” she told the Nine network.

The collapse of the sign – which was bolted and welded to the gantry – prompted an inquiry involving the Major Roads Project Authority, Transurban, their contractor and VicRoads.

The Calder Freeway, Bolte Bridge and West Gate Freeway were all closed on Wednesday night as safety audits were carried out on several overhead signs and gantries.

“We’re relieved to find that through those audits that we’ve identified no problems with any of those signs which gives us comfort,” VicRoads’ Robyn Seymour told reporters on Thursday.

Ms Seymour expects further audits of signs on the West Gate, Monash and Eastern freeways but said it was too early to say how the sign fell onto Ms Lettieri’s car.