The three were killed when a station wagon and a ute collided at the intersection of Mitcham and Hepburns Road shortly after 10am.
Police said the crash happened at high speed.
Police today named the three killed as 30-year-old Chante Alissa Harmer, 19-month-old Te Awanuiarangi Shayelous-Jay Matenga Tapiata-Harmer and eight-month-old Wysdom Amara Francis Tony Jane Tapiata-Harmer.
A Givealittle page has been set-up following the crash by Ashleigh Harmer, the cousin of killed woman Chante Harmer.
Ms Harmer said the crash had also killed Chante's two youngest children and "rocked us a whanau".
"My poor cousin Chante and her two youngest children were tragically killed in the car accident that occurred in Ashburton [yesterday] morning.
"To give you a sense of the kind of person that Chante was; she was kind, caring and generous with the little that she had. She is and will always be known as a person who had the biggest heart."
She said Chante and the two children would be buried in Hawke's Bay alongside one of Chante's sons who died from sudden infant death syndrome in 2006.
The funds raised would be used to bring the bodies to Hawke's Bay and pay for funeral costs.
Any remaining money would be used to support her four remaining children.
The New Zealand Herald reported family was travelling in a green Holden Astra, heading north along Hepburns Rd, which is controlled by give way signs.
A fourth person, a teenager, also suffered critical injuries in the crash.
The second vehicle, a white Ford Ranger, was heading west along Mitcham Rd.
The Ranger driver suffered moderate injuries.
Hepburns Rd resident Brad Fallaver said people use the road as a detour to avoid Ashburton town.
He said unless drivers knew the road well, at 100 kilometres an hour, the intersection at Mitcham could surprise them.
"At the intersection itself there's the give way signs but I guess back further, normally they tell you there's a give way coming. If they're unfamiliar and speeding along perhaps they got to that intersection before they knew it."
He said locals knew to stop because it could be hard to see if traffic was coming.
"If you're coming from Ashburton and heading toward Christchurch you've got to poke your nose out a fair bit to get a look of what's coming up Mitcham."
Mr Fallaver said a part of Hepburns Road was gravel and could be hard to stop if hit at speed.
ODT, NZME and RNZ
