An ambulance spokesman said the driver was found in cardiac arrest and no other vehicles appeared to be involved.
The serious crash unit is investigating and the name of the driver will be released once family have been advised.
Later in the afternoon, a motorcycle rider died after a collision with a car near Cambridge.
The rider died at the scene and the driver of the vehicle was taken in a serious condition to Waikato Hospital, a police spokesman said.
The road was closed for two hours and diversions were put in place.
Meanwhile, in Tokoroa police were interviewing a woman after a 20-year-old man was stuck by a car about noon. He was airlifted to Waikato Hospital in a critical condition.
"We are investigating the circumstances which led to his injuries and are currently speaking with a woman who is known to the injured man in relation to the incident," a police spokesman added.