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How to Investigate an Accident at Work

By: Norman Thomson - Updated: 19 Aug 2015 | comments*Discuss
Accidents Witnesses Work Interviews

The Importance of Accident Investigation

Determining the cause of workplace accidents is extremely important. It is essential that even minor accidents are reported and properly investigated so that causes are identified and control measures put in place to prevent recurrence.

One of the most important aspects of accident investigation is determining the underlying causes of the accident. Often, people stop the investigation too early, forgetting that each main cause may have several underlying causes. For example, if a person slips on a wet floor and injures themselves, some people would say the ‘cause’ of the accident was the wet floor. This is correct, but we say this is the IMMEDIATE CAUSE.

What is more important are the underlying causes, or ROOT CAUSES. For example, what caused the water to be left lying on the floor, did the water come from a leak, had the water been lying on the floor for several minutes or several hours – or even days – before the accident?

These questions, and of course their answers, are more beneficial than the actual immediate cause itself. We can learn more about the safety culture of an organisation by investigating root causes, than we can by any other means. Therefore, carrying out an in-depth investigation, which goes beyond the immediate cause, is not only essential; it is very beneficial in the long-term.

The Five Stages of an Accident Investigation

  • Reporting
  • Gathering information
  • Analysing information
  • Identifying risk control measures
  • Action planning and implementing


After an accident occurs, it is important that it is reported properly. In most cases, accidents only need to be reported internally, i.e. kept within the company or organisation. However, there are certain types of accident that need to be reported to the Health and Safety Executive (HSE), or the Local Authority. These ‘statutory reportable cases’ are found in a piece of health and safety law known as the Reporting of Injury Disease and Dangerous Occurrences Regulations (RIDDOR). This law requires employers to report certain accidents by telephone (or via the internet) within 24 hours of the accident occurring. Also, the accident should be reported to the authority on a special form and submitted within 7 days of the accident.

Gathering Information

The next step is to gather information about the accident and about the events that led up to the accident. Interviews with people who were injured or involved are essential. Interviews may also need to be conducted with people who supervise the area where the accident occurred. Drawings and photographs are a good way of recording the scene of the accident. Things to consider during the information gathering stage are:

  • What happened?
  • Who was involved?
  • What equipment was being used at the time?
  • Were procedures being followed at the time and, if so, copies of those procedures should be looked at?
  • What was the injured person actually doing at the time of the accident and immediately before the accident?
  • How did the injury occur?
  • Were any first aid measures taken and, if so, by whom?
  • Who was the site supervisor?
  • Were there any witnesses?
  • What personal protective equipment was being worn at the time of the accident?
  • What was the sequence of events that led up to the accident?

This final point is an important one. It is essential for anyone who investigates an accident to fully understand the sequence of events. An accident often occurs, not because of the immediate thing that went wrong, but because of something much earlier going wrong.

Analysing the Information

Once information has been gathered, it should be analysed thoroughly. This is the stage when the investigator can start to piece together the sequence of events and to start understanding why the incident occurred and, more importantly, the underlying reasons for the accident.

Many accident investigators use a ‘tree’ diagram to show the events that led up to the accident. This technique puts the accident at the top of the tree and the branches that come from the top show the contributing factors. In fact, this is why the main causes of an accident are caused the ROOT cause – the root of the tree feeds its growth. The root causes of the accident contribute towards the final accident. Cut off the root and the plant dies! By identifying the root cause of an accident, and then by eliminating that cause, the accident can never happen again.

Identifying Risk Control Measures

After the accident has been analysed and the root causes have been identified, control measures can be identified that will ‘cut off the root’. Control measures cover many different aspects of health and safety and can include: personal protective equipment; training of personnel; procedures for doing the job; better equipment; improved maintenance; and improved safety inspections.

Action Planning and Implementing

The final stage of the accident investigation is to ensure that a plan is put together for implementing the control measures that have been identified.

By following the five stages of accident investigation, employers can greatly improve workplace safety. Unfortunately, often it takes an injury for lessons to be learned, but at least if an injury does occur, the event can be used to help increase the standard of health and safety at work.

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[Add a Comment]
abdul - Your Question:
Two cctv footage been recording an accident at work and no witness only cctv and the company wont give cctv to the court and the person hasnt been trained to use the mashine and they lie and say they tell him dont use the mashine what can I do on this matter to gey justice done.? please help

Our Response:
I suggest in this instance you contact the HSE directly via the link here. I hope this helps.
WorkplaceSafetyAdvice - 20-Aug-15 @ 10:23 AM
two cctv footage been recording an accident at work and no witness only cctv and the company wont give cctv to the court and the person hasnt been trained to use the mashine and they lie and say they tell him dont use the mashine what can i do on this matter to gey justice done.? please help
abdul - 19-Aug-15 @ 2:14 AM
@kentoz - we're glad you find the site informative.
WorkplaceSafetyAdvice - 31-Oct-14 @ 2:48 PM
there is clarity in the information given and completeness as welll.
kentoz - 31-Oct-14 @ 5:56 AM
Very well explained and easy to understand, credit to Norman Thomson.
Abdul - 24-Apr-13 @ 3:33 PM
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