A massive drop-out on State Highway 4 happened so quickly it was lucky no vehicles were swept away by it, says Higgins worker Paul Seconi.
It's his job to guard the ever-expanding drop-out that has closed a lane of the highway just south of Upokongaro.
Mr Seconi said the slip opened up a couple of weeks ago and began as a small crack in the road.
"A truckie noticed a crack in the road about 5am and by 9am this side of the road had gone," Mr Seconi said.
Higgins staff were keeping a round-the-clock watch on the drop-out as it was still moving.