Michal Kopaniarz, of Park Road, Donnington, entered guilty pleas at Winchester Crown Court to three charges of causing death by dangerous driving.
The 40-year-old also admitted perverting the course of justice by destroying a Samsung mobile he was using at the time of the smash, which happened on the A303 near Andover, Hampshire, on August 25 2021.
A Hampshire police spokesman said previously: “The collision involved a Vauxhall Astra, a Mercedes food delivery van, a HGV and a DAF recovery truck.
“Sadly, Alex Britton, 28, from Fifth Avenue, Portsmouth, Tina Ince, 58, from Lydgate Road, Southampton, and Tom Watson, 30, from Cheriton Avenue, Southampton, all from separate vehicles, were pronounced dead at the scene.”
Simon Jones, prosecuting, told the court: “This defendant knew in August 2021 that it was his dangerous driving that caused the death of three people and he knew that his destruction of his phone was done with a specific purpose.”
Samantha Ball, defending, said: “Mr Kopaniarz is taking full responsibility for what happened that day.”
Judge Angela Morris adjourned the case for sentencing on February 24 and remanded Kopaniarz in custody until then.
She also imposed an interim driving disqualification.
She said Kopaniarz “knew he would be pleading guilty” in what is a “very sensitive and serious case” and arrived at court promptly.
“But having now pleaded guilty to such serious matters as these, I note there have been concerns in relation to his mental health, quite understandably given the nature of the offences he has pleaded guilty to,” she said.
“It seems to me in those circumstances that bail must be withdrawn at this stage. The defendant will now be remanded in custody.”