The ordering of an investigation and preservation of evidence will also undergo some changes as well as an effort to improve readability. In short, accidents involving both passenger and cargo vessels greater than 500gt will remain mandatory while investigations into smaller vessels will become discretionary. This is to allow the MAIB to allocate resources to those accidents with the greatest potential for safety learning. Further, the requirement to conduct preliminary investigations for every marine casualty will be removed along with the requirement to begin an investigation within 2 months. However, the inspector will retain the power to gather evidence prior to making the decision to investigate and will still have to begin an investigation as soon as reasonably possible. Similarly, there is now only a requirement to record the reasons for turning down an investigation, not the details of any decision.