The Barr government's ground-up reforms of the ACT's compulsory third party insurance will be tabled in the Legislative Assembly on Tuesday, more than 18 months after a citizen's jury on the topic was first announced.

Under the new scheme, everyone injured in a motor vehicle accident will be entitled to up to five years of medical treatment, care and lost income, as long as they were not breaking the law at the time of the accident.

People who are assessed with an injury severity of 10 per cent whole person impairment or higher will be able to pursue damages through the legal system if they still need treatment after their five years of defined benefits.

"Every one of Canberra’s 290,000 drivers has to pay for CTP with their annual registration, so we believe everyone who gets injured on the road should be covered," Chief Minister Andrew Barr will tell the Assembly on Tuesday.

"That’s the fundamental, significant change this bill will make - to ensure everyone who is injured in a motor vehicle accident is entitled to the treatment, care and support they need to get better and get their lives back on track."

However savings to premiums will not be as great as expected, after the pool of common law claimants was widened.

The Greens refused to back the reforms unless big changes were made to the legislation, amid concerns about "harsh outcomes" from the whole-of-person impairment test, especially for injured children and workers who could no longer do their former jobs.

As a result, injured children who still need treatment after four years and six months will be able to pursue benefits through the common law system, even if they do not meet the 10 per cent whole person impairment threshold.

Injured workers who don't meet the threshold but have been unable to retrain or find new employment after retraining can also pursue common law damages through the courts, if an independent medical assessment confirms their incapacity to work.

Due to the changes, some of the cost savings from the proposed scheme will be eroded.

However Greens crossbencher Caroline Le Couteur said the amended scheme would still be viable.

"We understand there will still be an overall reduction in premiums in the new scheme, but it won’t be as great as the one expected under the government’s initial model after some of the concessions we secured have been factored in," Ms Le Couteur said.

"The Greens view on this is that we don’t want premium reductions to come at the expense of appropriate health outcomes for individuals. We favour a system that is fair and compensates people adequately, even if this means premiums are a little more expensive than they could otherwise be.

"We believe that most people in Canberra will support a smaller reduction in premiums if they know this helps victims receive fair compensation.”

Separately, injured adults who still need medical treatment after five years can pursue a lump sum payment from their insurer through ACAT. This would apply to people who were not-at-fault and who do not meet the 10 per cent threshold. It would also only apply to future medical costs.

Benefits would also no longer be restricted or removed for people injured while committing minor traffic offences, including cyclists who were not wearing a helmet and drivers whose passenger was not wearing a seatbelt.

However the concession also extends to drivers who may have tested positive for past use of cannabis through a blood test, but who were not impaired at the time of the crash.

Claimants will also be able to challenge their insurers' decisions through ACAT if an internal review fails. A new division of the administrative tribunal will be set up to deal with the claims.

People who are of retirement age but were still working at the time of their accident will be able to access defined benefit income replacement payments for up to two years.

Workers injured in a motor vehicle on the job will now have up to 13 weeks to decide whether to receive benefits through the workers compensation scheme or CTP scheme, and would not be locked into either.

Changes to the bill would also make it more difficult for insurers to reject late applications for compensation, enabling people to claim they did not receive timely or accurate information about the application process as a permissible excuse.

"We think this will incentivise insurers to disseminate information about the CTP process and correct a potential scenario where insurers benefit by allowing there to be a CTP knowledge gap in the community," Ms Le Couteur said.