This is the terrifying moment a huge concrete slab plunged from a new flyover being built onto the road below.

Dashcam footage shows the chunk plummeting into oncoming traffic - with a driver having to swerve to avoid being crushed on the Rama II road in Bangkok, Thailand, on May 7.

Local media reported that the slings supporting the concrete segment snapped, causing it to fall. Four vehicles were damaged in the incident.

Police Colonel Lertsak Kheamsap, superintendent of the Tha Kham Police Station, has ordered an investigation into the blunder.

Expressway Authority of Thailand (EXAT) governor Surachet Laophulsuk has also suspended the construction for seven days for the probe. He added compensation will be given by EXAT to the affected drivers.