A crash involving a vanload of people near Mercer yesterday occurred when a car travelling towards Auckland crossed the median strip and ploughed into the south-bound vehicle, police say.
Waikato road policing manager inspector Freda Grace said early indications were that a blue hatchback driven by a woman who was the sole occupant crossed over the grass median strip and collided with a south-bound van carrying 12 people, some of them tourists.
The van was returning to Rotorua, after its occupants had picked up friends from America who had arrived in New Zealand on Monday, when the crash happened just before 1pm.
The blue hatchback smashed into the front of the van on the Waikato Expressway, about 1km south of the Meremere Dragway.
Ms Grace said the crash was still under investigation and it was not known whether seat belts, a medical condition or distraction were factors.
St John Northern duty centre manager Norm Ngatai said paramedics treated 13 people at the scene, but only four - including the drivers of both vehicles - had to be taken to hospital.
The Westpac Rescue Helicopter airlifted two women from the van - one with moderate chest injuries and the other with moderate spinal injuries - to Waikato Hospital. Another person with minor injuries was taken to Waikato Hospital, and the fourth patient was taken to Middlemore Hospital.
Ms Grace said the crash was a good reminder to drivers to make sure there were no distractions such as mobile phones before they set off and for everyone to wear seat belts.