Bradley Payne, 28, died on the A5 southbound between the junctions of Caldecotte and Fenny Stratford on Saturday, March 13.
He had pulled up to change a tyre on his van when he was involved in a collision with a car, say his heartbroken family.
Bradley (pictured) was dad to two little girls. His partner is pregnant.
His mum Sharon Payne said: “Bradley was our fourth child and the centre of our family. Nothing was more important to him than family.
“He worked hard as a scaffolder and bought his own home. Since his death we have been inundated with the most wonderful messages of love and respect for him.”
Bradley was a former pupil at Cardinal Newman School and after years as a scaffolder, he was working for Network Rail at the time of his death.
Family friend Chelsey Usher created a fundraising page with the aim of raising enough cash to pay for Bradley’s funeral and help support his children.
Yesterday (Tuesday), the page reached its goal of £8,000 on what would have been Bradley's 29th birthday.
Chelsey said: "It's been absolutely amazing and the way everybody has pulled together to help support Bradley's family has really touched us all.
"Bradley was just the nicest person and such a good dad, I don't know anyone who had a bad word to say about him.
"If I could just say a massive thank you to everyone! I've been on the phone to his mum and she's overwhelmed by their support."
You can view the fundraising page for Bradley at GoFundMe.