Two cars repeatedly drift in and out of their lanes on a busy motorway in Ireland in a video taken by a shocked man in another vehicle.

In the video, filmed last month on a mobile phone on the southbound M50 near Ballymun, Dublin, a white van and what appears to be a silver Volkswagen Passat seem to be racing each other, forcing the other out of their lane.

The incredibly dangerous display of driving continues for more than 30 seconds before the two vehicles eventually exit the motorway and out of view.

The shocked filmer says the local police were made aware of the incident of the video.

Writing on social media at the time, the filmer writes: "Check out these two idiots on the M50. They should be banned for life."

Local media said the incident took place near the Finglas exit at Junction 5.

It took place on the M50 near Ballymun. I work all over Dublin so I spend a lot of time on that road. The cops are aware of the vid as it was also sent to them. This was taken on the phone on the phone holder.