Dramatic footage has emerged of the moment a digger struck the Penrose overbridge, bringing Auckland motorway traffic to a standstill for several hours.

The digger was being transported by a truck when its arm struck the overbridge about 1.15pm on Monday.

Waitemata police are investigating the incident and are considering whether to lay charges.

The police motorway team was reviewing CCTV footage and statements from witnesses and those directly involved in the crash.

Police have confirmed that the load was over-height and witnesses have described seeing the high-visibility LED early warning signs activate as the truck approached to the bridge.