"He did not have time to brake or take evasive action, and his car was hit by the Nissan Sunny," the finding said.
Mr Carr and his granddaughter were injured but Mr Carr was able to get out and check the Nissan.
"When he looked into the vehicle, it appeared that both girls were dead. He put a blanket over the side of the car and rang the police."
The crash occurred in light traffic on a road described as "snaking followed by straight sections". The Nissan was not found to have any defects and, while it had been raining, it was not at the time. Neither woman had alcohol or drugs in their system.
"The underlining lesson for all who may review this case is to drive to the conditions of both the road and the weather on the day," Mr Shortland said.
"Irrespective if the driver is from overseas, New Zealand-wide or a local who may be familiar with the road, it is important to drive to the conditions."