Root Cause Analysis (RCA) is a systematic process used to determine why a workplace accident, incident, injury, near miss, equipment failure, or other unwanted event occurred. Instead of stopping at the immediate cause of an incident, Root Cause Analysis looks deeper to identify the underlying conditions, decisions, procedures, or safety-management failures that allowed the incident to occur.
In workplace safety, identifying the root cause is important because correcting only the immediate problem may prevent the exact same event temporarily without eliminating the conditions that created it.
For example, if an employee slips on oil on the floor, cleaning up the oil addresses the immediate hazard. A Root Cause Analysis asks additional questions: Where did the oil come from? Why did the leak occur? Why wasn’t it detected? Why wasn’t the spill cleaned up before someone was exposed to it? Does the company have an effective inspection and preventive-maintenance system?
The answers may reveal that the real problem is not simply oil on the floor, but an inadequate equipment inspection or maintenance process.
This systems-based approach is consistent with OSHA’s guidance. OSHA encourages employers to investigate injuries and illnesses as well as close calls or near misses and to identify and correct root causes rather than focusing on fault or blame.
What Is a Root Cause?
A root cause is an underlying or system-related reason an incident occurred that identifies a correctable failure. An incident may have one root cause or several contributing root causes.
Root causes frequently involve weaknesses in areas such as:
- Safety procedures and work practices
- Employee training or competency
- Supervision and accountability
- Equipment design, inspection, or maintenance
- Hazard identification and risk assessment
- Job planning and communication
- Management systems and policies
- Staffing, scheduling, or workload
- Procurement or equipment selection
- Change management
- Corrective-action systems
- Previous hazards that were identified but not corrected
A useful Root Cause Analysis therefore goes beyond asking what happened. It asks why it happened and what allowed it to happen.
Root Cause Analysis vs. Incident Investigation
Incident investigation and Root Cause Analysis are closely related, but they are not exactly the same thing.
An incident investigation is the overall process of gathering and evaluating information about an event. It may include securing the scene, interviewing employees and witnesses, reviewing photographs and records, examining equipment, reconstructing the sequence of events, determining causal factors, identifying root causes, developing corrective actions, and documenting the investigation.
Root Cause Analysis is the part of the investigation that digs beneath the immediate causes to determine the underlying reasons the event was able to occur.
OSHA recommends investigating not only injuries and illnesses but also close calls or near misses because they can reveal hazards and weaknesses before someone is seriously injured.
Immediate Causes, Contributing Factors and Root Causes
A good workplace incident investigation should distinguish between what happened immediately before an incident and the deeper factors that made the event possible.
Consider an employee who falls from a ladder.
Immediate Cause:
The ladder shifted while the employee was climbing.
Contributing Factors:
The ladder was positioned on an uneven surface and was not adequately stabilized.
Potential Root Causes:
The company had not established an adequate ladder setup procedure, employees had not received sufficient training, pre-use planning failed to identify the uneven surface, or supervisors were not verifying proper ladder setup.
Simply telling employees to “be more careful” would do little to correct these underlying problems.
This is why OSHA cautions against ending an investigation with conclusions such as employee carelessness or failure to follow a procedure. A stronger investigation asks why the behavior or condition existed and what system changes could prevent it from recurring.
How to Perform a Root Cause Analysis
The complexity of a Root Cause Analysis should reflect the seriousness and complexity of the incident. A minor near miss may require a relatively simple analysis, while a serious injury, equipment failure, fire, chemical release, or potentially catastrophic event may require a formal investigation team and more sophisticated analytical techniques.
A typical workplace Root Cause Analysis includes these steps:
- Respond to the incident and control immediate hazards.
Provide medical assistance when necessary, protect employees from continuing hazards, notify appropriate personnel, and secure the incident area when appropriate. - Gather information.
Collect the facts before reaching conclusions. Information may include employee and witness interviews, photographs, video, equipment records, training records, JSAs, procedures, inspection records, maintenance records, permits, SDSs, and other relevant documentation. - Determine what happened.
Establish the sequence of events leading up to, during, and immediately following the incident. - Identify immediate and contributing causes.
Determine the conditions, actions, equipment failures, environmental factors, or other circumstances directly associated with the event. - Identify the root cause or root causes.
Continue asking why the contributing factors existed. Look for underlying failures involving procedures, training, planning, supervision, equipment, maintenance, communication, hazard recognition, or management systems. - Develop corrective actions.
Corrective actions should address the identified root causes rather than merely the symptoms of the problem. - Assign responsibility and completion dates.
Each corrective action should have an accountable person and a target completion date. OSHA’s incident-investigation guidance specifically recommends assigning responsibility and tracking corrective actions through completion. - Verify effectiveness.
Follow up after corrective actions are implemented to determine whether they actually eliminated or adequately controlled the underlying problem.
The 5 Whys Root Cause Analysis Method
One of the simplest methods of Root Cause Analysis is the 5 Whys.
The investigator repeatedly asks “Why?” until the underlying reason for the problem becomes apparent. Despite the name, exactly five questions are not required. Some problems may take three questions; more complicated incidents may require considerably more.
OSHA includes the Five Whys as a tool for investigating workplace incidents and finding root causes.
For example:
Incident: An employee slips on hydraulic oil.
Why did the employee slip?
There was oil on the walking surface.
Why was oil on the walking surface?
A hydraulic hose was leaking.
Why was the hose leaking?
The hose had deteriorated.
Why wasn’t the deteriorated hose replaced?
Its condition had not been identified during equipment inspections.
Why wasn’t it identified?
The preventive-maintenance inspection did not include an adequate inspection of hydraulic hoses.
The analysis has now moved from:
“Employee slipped on oil.”
to:
“The preventive-maintenance and inspection system did not adequately identify deteriorating hydraulic hoses.”
The second conclusion provides a much better basis for preventing another incident.
Root Cause Analysis Questions
Investigators should keep an open mind and avoid deciding on a cause before the evidence has been collected.
Useful questions include:
What happened?
What task was being performed? What was supposed to happen? What actually happened? What changed?
Why did it happen?
What conditions or actions contributed? Why were those conditions present?
Equipment:
Was the correct equipment being used? Was it properly maintained? Had defects been previously reported? Were safeguards working?
Procedures:
Was there an established procedure? Was it adequate? Was it practical? Was it understood and followed?
Training:
Had employees received appropriate training? Had they demonstrated competency? Was refresher training necessary?
Supervision:
Was the work adequately planned and supervised? Were unsafe conditions or practices previously observed?
Hazard Recognition:
Was a Job Safety Analysis or other hazard assessment performed? Was the hazard foreseeable? Had similar hazards previously been identified?
Management Systems:
Were there deficiencies in inspection, maintenance, purchasing, staffing, communication, scheduling, corrective actions, or other management processes?
OSHA specifically recommends asking questions such as why equipment failed, whether it had been properly maintained, whether employees had appropriate tools and sufficient time, whether they were adequately trained, and whether they were properly supervised.
Root Cause Analysis Should Not Be About Blame
An effective Root Cause Analysis is not an exercise in assigning blame.
Stopping an investigation with statements such as “employee error,” “carelessness,” or “failure to follow procedures” may overlook the conditions that influenced the employee’s actions.
If an employee did not follow a procedure, the investigation should ask:
Why wasn’t the procedure followed?
Was the employee properly trained?
Was the procedure practical for the work being performed?
Was the procedure current?
Was the correct equipment available?
Was adequate time provided?
Had supervisors previously observed the same practice?
Were production or scheduling pressures influencing the work?
Had the hazard previously been identified?
This does not mean individual actions are irrelevant. They can be important contributing factors. The objective is to understand why those actions occurred and what can reasonably be changed to prevent recurrence.
OSHA emphasizes this same principle, recommending that incident investigations focus on identifying and correcting root causes rather than finding fault or blame.
Root Cause Analysis for Near Misses
A serious injury does not have to occur before a Root Cause Analysis is useful.
Near misses can provide valuable information because the underlying hazards may be nearly identical to those involved in an injury-producing incident—the outcome was simply different.
Examples may include:
A suspended load falls but misses employees.
A forklift nearly strikes a pedestrian.
An employee trips but catches themselves before falling.
A trench wall partially collapses while no one is inside.
A machine unexpectedly energizes during maintenance but no employee is injured.
A combustible-gas monitor alarms before an ignition occurs.
Investigating these events gives employers an opportunity to identify and correct weaknesses before a similar event causes an injury or fatality. OSHA’s Recommended Practices specifically encourage employers to investigate close calls and near misses as part of hazard identification and assessment.
Root Cause Analysis and Corrective Actions
Finding the root cause is only useful if something is done with the information.
Corrective actions should be specific to the causes identified and, where feasible, should favor controls that eliminate or reduce the hazard rather than relying solely on employee behavior.
Depending on the findings, corrective actions might include:
Engineering changes, equipment replacement or guarding; revised preventive-maintenance schedules; new inspection requirements; changes to work procedures or JSAs; additional training or competency verification; improved supervision; physical barriers or access controls; changes in purchasing specifications; improved communication; or revisions to the company’s safety program.
Corrective actions should be assigned, tracked, completed, documented, and evaluated for effectiveness.
Root Cause Analysis Example
Consider a warehouse employee who is nearly struck by a forklift at the end of an aisle.
A superficial investigation might conclude:
Cause: Employee wasn’t paying attention.
A Root Cause Analysis would examine the situation more thoroughly.
The investigation might find that the intersection had obstructed visibility, there was no designated pedestrian crossing, forklift and pedestrian routes overlapped, employees routinely crossed at that location, and no physical barrier or traffic-control system had been installed.
The investigation might therefore identify several root or system causes, including inadequate pedestrian/vehicle traffic planning and workplace hazard assessment.
Corrective actions could include redesigning pedestrian routes, installing barriers, establishing marked crossings, improving visibility, revising forklift procedures, and training affected employees.
Those changes address the conditions that created the near miss instead of simply instructing everyone to “pay more attention.”
Root Cause Analysis Form
A standardized Root Cause Analysis Form can help ensure investigations consistently address both immediate and underlying causes.
A workplace RCA form may include:
Incident Information — date, time, location, employees involved and type of event.
Incident Description — factual description of what occurred.
Evidence Collected — photographs, statements, equipment records, training records, procedures and other documentation.
Immediate Causes — conditions or actions directly associated with the event.
Contributing Factors — circumstances that increased the likelihood or severity of the incident.
5 Whys Analysis — structured questioning used to explore underlying causes.
Root Cause(s) — identified system or process failures.
Corrective Actions — actions necessary to eliminate or control the causes.
Responsible Person and Due Date — accountability for completing each corrective action.
Verification and Follow-Up — confirmation that corrective actions were completed and effective.
OSHA recommends that employers establish an incident-investigation procedure in advance, including who will participate, lines of communication, necessary equipment and supplies, and reporting forms and templates.
Root Cause Analysis and Workplace Safety Programs
Root Cause Analysis should not operate independently from the rest of a company’s safety program.
Investigation findings can reveal deficiencies that require changes to:
- Job Safety Analyses (JSAs)
- Safety inspections and audits
- Employee training
- Equipment inspection and maintenance
- Hazard Communication
- Lockout/Tagout procedures
- PPE requirements
- Emergency procedures
- Written safety programs
- Supervisor responsibilities
- Corrective-action tracking
Incident trends can also reveal broader problems that may not be obvious when incidents are considered individually.
OSHA recommends grouping similar incidents and looking for trends in injuries, illnesses, hazards, and near misses as part of an ongoing hazard-identification process.
Root Cause Analysis and OSHA
OSHA encourages employers to use Root Cause Analysis during incident investigations because identifying the underlying reasons an incident occurred can help prevent the same or similar event from happening again.
It is important, however, not to present Root Cause Analysis itself as a universal stand-alone OSHA requirement for every workplace incident.
Certain OSHA standards contain specific incident-investigation requirements. For example, employers covered by OSHA’s Process Safety Management (PSM) standard have incident-investigation obligations for incidents that resulted in, or could reasonably have resulted in, a catastrophic release of a highly hazardous chemical. OSHA also broadly recommends root-cause-focused investigations as an effective safety-management practice.
Employers should determine which OSHA reporting, recordkeeping, investigation, and industry-specific requirements apply to each incident.
Building a Stronger Safety Program Through Root Cause Analysis
The ultimate purpose of Root Cause Analysis is prevention.
Workplace incidents, injuries, equipment failures, property damage, and near misses provide information about how a safety system is performing. A thorough investigation uses that information to determine what happened, why it happened, what underlying weaknesses contributed to it, and what should change.
When employers investigate beyond the immediate cause, implement meaningful corrective actions, and verify that those actions are effective, Root Cause Analysis becomes more than an investigation technique. It becomes an important part of a proactive workplace safety and health program.
OSHA’s Recommended Practices similarly emphasize identifying hazards, investigating incidents and near misses, determining root causes, implementing controls, and evaluating whether those controls remain effective.
Develop a consistent process for reporting and investigating workplace accidents, incidents, injuries and near misses. A comprehensive Accident/Incident Investigation Safety Program can establish responsibilities and procedures for gathering information, identifying immediate and root causes, developing corrective actions, tracking completion, and helping prevent similar incidents from occurring again.
Available as an individual safety program or as part of a complete OSHA Safety Manual.