Driver Philip Potter, 19, was arrested on suspicion of causing death by dangerous driving and manslaughter by gross negligence.
Four people died after being struck by the Scania truck on Lansdown Lane in Upper Weston, Bath, Somerset, just after 4pm on February 9.
The red truck first hit and killed Mitzi Rosanna Steady, four, from Bath, and her grandmother, who remains in a critical condition in Southmead Hospital in Bristol.
It went on to collide with a number of other vehicles on the road before overturning on to a Volvo at the bottom of the hill, killing the three men inside.
They were Robert Parker, 59, from Cwmbran, electricity company director Philip Allen, 52, and taxi driver Stephen Vaughan, 34, both from Swansea.
Avon and Somerset Police arrested Potter, from Brinkworth, Wiltshire, yesterday morning, along with a 28-year-old man, believed to be his boss.
A force spokesman said: “The two men arrested in connection with the fatal road traffic collision in Bath last Monday have been released on bail.
“The arrests follow the incident on Lansdown Lane on February 9 when a tipper truck carrying aggregate was in collision with a number of vehicles and two pedestrians.
“Four people died as a result of the incident.
“A 19-year-old man was arrested on suspicion of causing death by dangerous driving and manslaughter by gross negligence.
“A 28-year-old man was arrested on suspicion of causing manslaughter by gross negligence. Both have now been released on police bail pending further inquiries.”
Tributes have been paid to the victims of the incident by their families and friends, while mourners have laid flowers at a church near the scene.
Mitzi’s family released a photograph of the little girl and said: “Mitzi Rosanna Steady, aged four, loved and missed by us all.”
Staff at Snapdragons Nursery in Weston, which Mitzi attended, said: “We will always miss her smile and her warmth.”
A JustGiving page in memory of the little girl, which was set up by her family on Sunday, has already raised more than £10,500 for road safety charity Brake.
The widow of Mr Vaughan, from Penyrheol, near Gorseinon, Swansea, and who ran luxury taxi firm EliteXecutive Travel, said she was “devastated”.
“Steve was infectious - when he smiled, the whole room would smile,” Mrs Vaugan said.
“Myself, Steve’s parents and family are very proud of the man he was, a true gentleman and we were so privileged to have been a part of his life.
“We are devastated that he was taken away from us so soon. We had only been married six months and I was honoured that he chose me to be his wife.”
Father-of-two Mr Allen, who lived in Loughor, Swansea, with wife Caroline was a resources and external affairs director for Cardiff-based Western Power Distribution.
Relatives comforting Mrs Allen, 53, said she was too distressed to speak to the media following his death.
Around 400 residents attended an hour-long prayer service for the victims at All Saints Church, Weston, last week.
Children, parents and grandparents lit candles and used colourful pens to write messages of condolence on white fabric.
Bereavement counselling was offered to children at Weston All Saints Primary School, some of whom witnessed the collision.