Accident Investigation

The prime objective of accident investigation is prevention. Finding the causes of an accident and taking steps to control or eliminate it can help prevent similar accidents from happening in the future. Accidents can rarely be attributed to a single cause. Work environment, job constraints, and supervisory or worker experience can all play a part. These factors must be examined to determine what role each had in causing the accident.

Once the causes are established, precautions must be identified and implemented to prevent a recurrence. Investigators must always keep in mind that effective accident investigation means fact-finding, not fault-finding.

To explain why and how an accident happened, investigators must collect information on the events that took place before and during the event. Investigators can then determine accident conditions by examining physical evidence and interviewing witnesses. Both of these steps are of equal importance and should be done as soon as possible to ensure complete accident investigation. Equally important is the need to document the steps that were taken immediately after the accident to deal with the emergency and to begin the investigation. It also identifies the forms to be used and the procedures to be followed within specified time frames.

In order for an investigation to be a valuable tool in accident prevention, three things must take place:

  • 1. the information gathered must be analyzed
  • 2. corrective action must be taken
  • 3. the action must be monitored for effectiveness.


Company health and safety programs should have the following items addressed in the requirements regarding accident investigation:

  • What kinds of accidents must be investigated?
  • Who should investigate what?
  • What training should investigators have?
  • Who reviews the investigation report and follows up on any observations or recommendations?
  • What should be investigated? Lost-time injuries? All injuries requiring medical aid? All accidents with more than $ X in property damage? Any accidents with a potential for serious injury or major financial loss?

Reportable accidents

In addition to accidents that result in injury, there are legal requirements to report accidents to the Ministry of Labour, Immigration, Training and Skills Development (MLITSD). These include fatalities, critical injuries, occupational illnesses, and the following prescribed incidents:

  • A worker falling a vertical distance of three metres or more.
  • A worker falling and having the fall arrested by a fall arrest system other than a fall restricting system.
  • A worker becoming unconscious for any reason.
  • Accidental contact by a worker or by a worker's tool or equipment with energized electrical equipment, installations or conductors.
  • Accidental contact by a crane, similar hoisting device, backhoe, power shovel, or other vehicle or equipment or its load with an energized electrical conductor rated at more than 750 volts. Structural failure of all or part of falsework designed by, or required by this Regulation to be designed by, a professional engineer.
  • Structural failure of a principal supporting member, including a column, beam, wall, or truss, of a structure.
  • Failure of all or part of the structural supports of a scaffold.
  • Structural failure of all or part of an earth- or water-retaining structure, including a failure of the temporary or permanent supports for a shaft, tunnel, caisson, cofferdam, or trench.
  • Failure of a wall of an excavation or of similar earthwork with respect to which a professional engineer has given a written opinion that the stability of the wall is such that no worker will be endangered by it.
  • Overturning or the structural failure of all or part of a crane or similar hoisting device.

There is a legal requirement to not only report what happened, but also the steps taken to prevent a recurrence. It is wise to investigate these events to see if they were the result of unforeseen, isolated circumstances, or if they resulted from a breakdown or oversight in the company's health and safety program.

The company's health & safety program should identify who should do the investigation and what training they are required to have completed. It should also identify who reviews the investigation report and who is responsible for ensuring that follow-up is done regarding any corrective actions/deficiencies that were found.


Did You Know?

IHSA offers an in-class Investigating and Reporting Incidents course. As well, the topic is covered in some of our other courses, including JHSC Certification—Part 1, Basics of Supervising.




Links to other topics


Links to existing IHSA and MOL material



The samples provided are intended to be modified to meet company or site-specific requirements. Without such modifications, they may not be appropriate. Although IHSA believes that the information provided is consistent with the legal requirements and/or good industry practices which prevailed at the time the information was compiled, users of this information are urged to check with current regulations, local/trade practices and the most recent edition of the reference material to ensure that it is still appropriate.


Last Updated: March 11, 2020