"It's only going to be a matter of time before someone is hurt or worse, killed.
"I hope no one ever has to see such a tragedy so that's why I sent this letter to you."
Jack's letter gained the attention of Kāpiti mayor K Gurunathan who contacted the council's roading team who checked out the intersection and decided a pedestrian refuge could be a viable solution.
The project was approved, the refuge, nicknamed Jack's Island, has been installed and a ceremony was conducted on Wednesday to officially open it.
Jack, 10, and Gurunathan cut a ribbon, held by Jack's mother Nicola Stephens and traffic engineer Gary Adams, and was watched by room one classmates.
"I spotted the letter and thought 'wow what a really great initiative'," Gurunathan told pupils.
"Safety is so important."
Teacher Vanessa Brewer said the area of roading at 3pm was "quite terrifying".
"Some kids don't make good choices when they're crossing this corner.