Driver Brett Andrew Button, 60, was sentenced in September to a maximum of 32 years behind bars over the crash in the NSW Hunter region in June 2023.
Survivors and family members of those who died have launched a class action against Transport for NSW alleging design failings in the roundabout. Button was driving while impaired by an opioid painkiller, taking 350mg of tramadol on the day of the crash despite doctors telling him the daily maximum dose was 200mg.
Court documents include allegations the interchange where the crash took place had numerous design flaws, such as being elliptical instead of round.