Queensland Police said the brick had come off the back of a passing truck when the family was travelling along the Warrego Highway in south west Queensland on Thursday afternoon.
Police said the projectile narrowly missed a 42 year old woman and an 8 year old boy when it tore through their vehicle with such force, it put a hole in the bonnet and roof before denting the trailer behind.
Both were treated for cuts from broken glass.
RACQ spokesperson Clare Hunter said the near-miss was a sobering reminder of the dangers of unsecured loads.
“It’s incredible no one was seriously hurt, but it just goes to show how dangerous an unsecured load is,” Ms Hunter said.
“It’s law that drivers must properly secure their loads to make sure they are safe.”
Ms Hunter said inadequately secured loads like foliage and building equipment could move during a drive, and this needed to be factored in by motorists.
“As the car is moving, the items in the tray or trailer can move around and settle, becoming unsecured – but it’s the driver’s responsibility to make sure the load isn’t a danger to anyone else,” she said.
Ms Hunter said there were stiff penalties for those who didn’t comply.
“In the overall scheme of things, a hefty fine could be the least of your problems. A wayward piece of building material or the like, could kill in an instant and the consequences become exponentially more serious,” she said.
“It’s everyone’s responsibility to ensure their vehicle doesn’t become a launching pad for a deadly missile.”