Both vehicles burst into flames, with the impact sending the car into a ditch and tipping Mr Stirling's truck on its side in the middle of the road.
The car had three occupants, 17-year-old driver Matthew McCann and two teenage passengers.
Mr Wiggins saw the crash in his rear view mirror and did a U-turn.
"I saw a teenage girl crawling out of the driver's side window ... she was screaming that her boyfriend was in the car."
A group of people rescued the trapped motorists.
He and Mr Kay then dashed to the truck, where Mr Stirling was almost obscured by thick smoke.
"I went to my van and grabbed a hammer," said Mr Wiggins, a carpetlayer.
"I smashed the window out and felt around inside and found him ... the whole cab was a blaze of orange."
Helped by Mr Kay, he pulled Mr Stirling from the cab just seconds before it was engulfed in flames.
Mr Wiggins said his reactions were instinctive and he never considered the danger until later.
"You see a fellow person in trouble like that and you just have to get in and do something."
Mr Stirling, who suffered grazes and a sore neck, went to see Mr Wiggins after he was discharged from hospital to thank him for what he did.
Mr Stirling said it was an incident that would be with him "forever" and was in no doubt that had it not been for the actions of the two rescuers he would not be here today.