There is an ongoing investigation into the engineering controls to see if there is some way to make sure an unattended vehicle can't move, removing the risk of human error.
In April, an employee suffered a fracture and a laceration to his finger after he slipped and cut it on a hedge trimmer he was using.
The report said the employee "removed his hand from the machine to steady himself" and in doing so, "his finger made contact with the moving blades".
The investigation has resulted in a new requirement for gloves to have a mechanical cut resistance rating of 5/5.
The fourth incident did not involve any accidents, but was still considered serious.
A horticulture and tree team were working together to prune branches in October 2016. Members of the public called Worksafe as the teams were working from the top of their toolbox behind the cab of the truck, without any fall protection in place.
WorkSafe went to the site and stopped the work until a new method was agreed upon.
The investigation showed there was inadequate planning before the work was started, the methods being used were not standard practice or compliant with industry guidelines, and traffic management was not good enough.
The report said there were 29 hazard categories where there was risk to council workers or those in the vicinity of council workplaces.
Eight of those categories have been identified as needing review over a two-year period.
The categories are personal confrontation or working alone, vehicles on and off the road, working at height, health and impairment, hazardous substances, working with or in the vicinity of services, asset failure, and other mobile equipment.