Richard Pusey, 42, has admitted to outraging public decency, reckless conduct endangering serious injury and drug possession.
Pusey, 42, had been pulled over for allegedly speeding when a truck swerved into the emergency lane, killing four police officers on April 22 last year.
In October, he was committed to stand trial after pleading not guilty to the same offences.
Pusey’s lawyer Dermot Dann QC said his client would now be seeking “significant credit” because he had admitted his guilt.
“Without his efforts to resolve this matter, it had the potential to drag on for years.”