ACT Policing were called to the river at Angle Crossing Road at 9.45am after the 75-year-old, detouring from an earlier accident on the Monaro Highway, was left stranded in fast moving flood water.

"With flood waters rising and emergency vehicles en route, professional kayakers on scene were able to use their safety equipment to rescue the man who had managed to get on the roof of the car," a police statement said.

Police said the driver, from Isabella Plains, had ignored two safety signs before driving into 1.5 metre-high water.

The elderly man was left wet but unharmed in the incident, police said.

The kayakers later assisted rangers by attaching their winch to the ute to pull it from the water.

The vehicle - not immediately tested against its advertised "unbreakable" status - was put on a truck and taken from the scene.

Police strongly urged motorists to obey all safety warnings and to not drive through flood waters.

A crash on the Monaro Highway around 8am led to four people being taken to hospital with a range of injuries, including chest, abdominal and leg injuries.

Traffic was delayed but resumed as normal about 12pm.