A woman in her 40's was airlifted to hospital in a critical condition after being hit by a truck near Turua in the Hauraki Plains on Wednesday

Auckland Westpac Rescue Helicopter Trust spokesperson says the woman suffered serious head and trauma injuries as a result of the incident which happened on Hauraki Road, south of Thames.

'At 11.52am the crew of W1 (Westpac 1) were tasked to Turua, South of Thames, for a female patient in her 40's who had been hit by a truck travelling at open road speed.

'She was flown to Waikato Hospital in a critical condition.”

A section of Hauraki Road from Orchard East Road to Piako Road was closed for several hours and was reopened by police at about 3.25pm.

The Serious Crash Unit is now investigating.