That was the scary realisation for Ami Gale.

The Sydney manufacturer was travelling in Camden man Greg Ackman's 1997 Mitsubishi Triton ute at 12.35pm on Saturday when half a brick was thrown through the windscreen.

Luckily for the 58-year-old, who was travelling at 100km/h, it was at the base of the windscreen.

``I saw like a shadow from the top (of the bridge) and `bang!','' Mr Gale said, reflecting on the weekend's horrifying event. ``I was so lucky that it hit the base of the windscreen if it had been 20cm higher, it would've penetrated the glass and onto my face.''

Usually Mr Gale, who was travelling north back to Sydney, would have been riding a scooter.

Fencing has been set up at the overpass by the RTA to try to prevent such attacks but Mr Gale believes cameras should be installed to ``deter this happening again''.

Mr Ackman agreed: ``If someone will have their picture taken (at these overpasses), then I think they'd think twice about doing it.''

An RTA spokesman said: ``The RTA has no plans to install security cameras on the overpass.''

Macquarie Fields local area command crime manager Mark Brett said police were always concerned about this type of behaviour.

``We encourage two things ensure your children aren't involved in throwing any sort of missiles, and if the motorist does see children or young people or any person undertaking such an incident, contact police immediately,'' Detective Chief Inspector Brett said.

If anyone has any information, contact police on 96050499.