Colin Bird was hospitalised for three days after the January 21 incident, which left him with internal bleeding, soft tissue damage to his stomach, a cracked rib, severe grazing to his left hand and a fractured L3 vertebrae.

He and partner Suzanne Latham were driving up the pass about 6.15am when the rock slammed on top of their Land Rover.

It hit the seam between the roof and the windscreen, broke the glass and dropped "agonisingly" onto Mr Bird's lap.

Mr Bird said there was no warning until the car suddenly paused and a deafening sound erupted.

"It wasn't like a normal accident where you think you're going to hit something and can prepare," Mr Bird said.

"The car just exploded. It literally sounded like something exploded.

"The steering wheel was smashed into pieces by the rock. Even though I was steering, I don't actually know if I had control or not."

Ms Latham is receiving ongoing physiotherapy for whiplash.

Multiple scratches on her forearms show where glass from the windscreen rained inward.

"When it happened, and the glass came in, I just thought, 'I'm going to hit the [rock] wall'," she said.

The car at first veered to the left and up the kerb, screeching along the rock wall until it bounced back onto the road and came to a stop.

Unable to see through the shattered windscreen, Mr Bird said he tried to steer the car to the left for fear of hitting oncoming traffic or driving off the pass.

The couple is grateful to three passers-by who came to their aid as they got out of the car, which has since been written off.

Mr Bird lay on the road and waited for an ambulance.

"He was white," Ms Latham said of her injured partner.

"He just said, 'hospital'."

Mr Bird has travelled on Bulli Pass just once since the accident, while Ms Latham is in no hurry to face it.

The rockfall occurred in light rain after two days of wet weather. Both say they will avoid the road during wet weather and question why it is not signposted to warn of the danger of rockfalls.

Roads and Maritime Services plans to close the pass on February 17 and 18 for "investigation work to inform future safety improvements".

An RMS spokesman would not respond to questions on whether any work had been done in the past to reduce the risk of rockfalls, or on how commonplace rockfalls were.

"Roads and Maritime Services is reviewing the circumstances surrounding the rockfall at this location," the spokesman said.

"A section of Bulli Pass will be closed next week to carry out an inspection of the location."