He told the inquest he was riding about 50 to 100 metres behind the leading bunch. It was his responsibility to warn the groups of approaching vehicles from behind.
But Mr Farrelly said he couldn't hear the truck that would later collide with his wife. He also couldn't yell loud enough for the riders in front to hear his warning.
"As our group began to climb a truck passed us so close I could have reached out and touched it," he said.
"The truck was definitely within an arm's reach, it gave me a fright that it was that close especially because it was so quiet."
He said Mrs Farrelly had trouble with her right shoe and was reaching down to adjust it.
She went away from the road's edge towards its centre when the passing truck either clipped her front wheel or handle bar.
"We saw the truck go straight through the bike which got spat out the other side," said Mr Farrelly.
He saw someone knocked over not knowing that the injured person was his wife as all the riders ahead were wearing the same apparel.
He saw Mrs Farrelly, his wife of 26 years, lying prone on the road, when he got closer.
Her cycling buddies put her into the recovery position but she never regained consciousness.
"Some time later the driver tried to make a brief appearance to us and tried to claim it was Jane's fault for turning towards the truck," said Mr Farrelly.
"In my mind Jane had come out more than a rider would...and more than a truck driver would be expecting but why was the truck driver trying to overtake in this situation?"
"These are generally truck drivers who are professionals and are seated higher. With the 100 metre rule he could not have seen 100m ahead, he was quite close when he overtook us."
The inquest before Coroner Gordon Matenga is set down for two days and will hear evidence from 14 witnesses including the truck driver.