The following description was taken from ARRB and Queensland Government:

Crash reduction factors (CRFs) are an essential data component in the evaluation and prioritisation of road projects, used primarily to estimate economic savings in crashes for proposed road improvement works. This allows for various potential design options to be compared, works programs to be prioritised, benefit-cost ratios to be estimated.
Queensland Transport and Main Roads maintains its own body of knowledge in relation to CRFs. This knowledge, contained in a CRF matrix, has evolved over time and as such a review was required to ensure its continued alignment with current best practice and knowledge.
This project involved a comprehensive review of the CRFs. Information was drawn from both local and international sources, including current practice and literature, as well as through the collective knowledge of the Australian Road Research Board (ARRB) and Transport and Main Roads representatives in a series of intensive workshops.