The 18-year-old, who has not been named, was seriously injured in an accident on the A90 between Crimond and the St Fergus Gas Terminal, Aberdeenshire, at 7:30am.
But it was 19-year-old Dylan Irvine who was killed in the same crash.
Mr Irvine was pronounced dead at the scene on Monday, while the 18-year-old is being treated in hospital and remains in critical condition.
Speaking to the BBC, Ch Insp Neil Lumsden said officers had been given incorrect information at the scene of the accident.
"Officers at the scene of a crash use every avenue available to help identify those involved as quickly and accurately as possible," he said.
He explained that police use personal items found at the scene of crashes to identify the people involved, as well as police and DVLA systems to find out who is insured to drive the vehicle.
"On this occasion, officers were faced with a confused scene including incorrect information provided by a witness.
"Once identified, the error was promptly corrected and the families of those involved were spoken to and were understanding of the circumstances.
"We have apologised to the families for any unintended upset and will review to identify any learning."
Yesterday, Mr Irvine's family paid tribute to him, describing him as "a loving son, brother and grandson, and was loved by all that had the pleasure of knowing him".
"He had an adventurous and outgoing soul and had the biggest heart," the family added.
Police have appealed for anyone with information about the incident to contact them.
Sgt Chris Smith, of the north road policing unit, said: "We are continuing to support the families of the two men, whilst we continue our investigations into the cause of the crash.
"I would again ask that anyone who has any information regarding the movements of the vehicle or the occupants, who hasn't already been spoken to by police, please contact us on 101, quoting incident number 0491 of Monday, 5 October 2020."