A man lost his wife and three of his children in a collision on Monday night.
More than 1,500 people have already donated to the fundraising page set up on Wednesday following the deaths of 29-year-old Zoe Powell, daughters Phoebe and Amelia, eight and four, and six-year-old son Simeon.
They were formally identified on Thursday.
The Powells, including husband and father Josh, 30, and their infant daughter, were travelling on the A40 on Monday night when their Subaru people carrier was in collision with a heavy goods vehicle near Oxford.
Thames Valley Police said Mr Powell and his youngest daughter are still in a “serious” condition in hospital, but they “are showing signs of improvement and are expected to make a recovery”.
The page, set up by Andrew Welsford, reads: “This is such a sad and tragic loss for a work colleague on the railway, whose family have been taken from him in a tragic car crash near Oxford.”
Referencing railway workers’ distinctive orange uniform, it added: “Many people in the world of the Orange Army will know Josh and I hope will contribute to give him some financial support when he needs later in recovery.”
Senior investigating officer Sergeant Dominic Mahon said the family wanted to thank those who had sent “kind sentiments” following the crash, in which he said Mr Powell was a passenger.
He said: “I would like to thank all those who have contacted police to provide witness statements and helped us with this investigation.
“Thank-you also to those that stopped at the scene to offer help at what was a very distressing incident.
“I would also like to extend this thanks, on behalf of the Powell family, to all those who have sent their kind sentiments to the force via our official channels.
“We know that this tragedy has affected not only the local community in Chinnor, but also the wider Oxfordshire community and across the country, and I would reiterate my personal thanks to all those who paid their respects to the victims, both online and in the village of Chinnor.”
Grieving friends, neighbours and colleagues described the Powells as “delightful”.
The tragedy came months after the family were forced into temporary accommodation when a fire broke out at their home in Chinnor, South Oxfordshire.
A statement from Chinnor Community Church, where the family were regular members of the congregation, said: “(The Powells) have been active, involved and much-loved members of Chinnor Community Church throughout their young lives.
“The news of the death of Zoe, Phoebe, Simeon and Amelia has shocked and saddened not just their church family here but also the whole community of Chinnor in which they were known and greatly loved.
“The family placed their belief in Jesus as Lord and Saviour, and we are confident that Zoe and the children are now safe in the arms of God.
“Our thoughts are with the family as we pray for healing and recovery for Josh and (his daughter).”
Police said they received multiple calls from members of the public at 9.50pm on Monday following the crash.
The HGV driver, a 56-year-old man, suffered minor injuries and has co-operated fully with the investigation, officers said.
There have been no arrests, and detectives have requested witnesses or those with dashcam footage to contact them.
Anyone wanting to donate to the crowdfunder is asked to visit justgiving.com/crowdfunding/andrew-welsford