'Hero truck driver' and 10yo boy help stop car crash on State Highway 1

The quick thinking of a 10-year-old boy and the kindness of a "hero truck driver" prevented a possibly fatal accident on State Highway 1 on Tuesday.

A post shared to the Counties Manukau Police Facebook page on Wednesday has detailed the "heartwarming tale" alongside a plea for the public's help in finding the unidentified "hero".

Police say Ryan and his nana, Kathie, were heading north on State Highway 1 between Meremere and Mercer when Kathie, the driver, started experiencing a medical emergency. 

"Ryan, who was in the front seat, noticed his nana slipping into a semi-conscious state," said police.

The 10-year-old immediately jumped into action, stepping over the vehicle's centre console to press on the brake. 

Although the car slowed, Ryan was unable to move his nana's foot from the accelerator. He started waving to passing motorists in a desperate bid for help as the car drifted closer to the crash barrier and the Waikato River.

"Thinking they were going to crash, Ryan managed to get the car to slow to a walking pace and jumped clear of the vehicle," said police.

At this point, a truck driver noticed Ryan waving for help and pulled over. 

"He ran to the vehicle, still moving at a walking pace, and managed to bring it to a standstill."

By the time St John arrived on the scene, the truck driver had left.

On Wednesday, Ryan and Kathie visited Sergeant Fleming at the Pokeno station. Kathie is recovering from Tuesday's health scare.

The duo's actions have received high praise from several Facebook users, with many commending Ryan's bravery and quick-thinking.

"Ryan's heroic effort helped to save his nana's life," said the post.

Police hope the truck driver will identify himself so he can be thanked for his actions. They ask anyone who may have an inkling of who the driver could be to come forward.