The RAC has raised concerns a new digital advertising sign on the Kwinana Freeway could result in a serious crash.

The sign at the Leach Highway overpass was erected despite a report by Aust Roads in 2013, highlighting the dangers of roadside advertising on driver distraction.

Main Roads is a member of Aust Roads.

RAC spokesman Will Golsby told Gary Adshead we need to limit in-attention.