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Policy on Occurrence Classification

Effective May 1, 2018, last revised February 24, 2021

1. Context

1.1 Each year, between 3000 and 4000 transportation occurrences are reported to the Transportation Safety Board of Canada (TSB) in accordance with the mandatory reporting requirements in the Transportation Safety Board Regulations (TSB Regulations). Numerous other events/occurrences are also reported to the TSB on a voluntary basis. Practical considerations dictate that only a small proportion of these occurrences can be fully investigated.

1.2 Section 7(1) of the Canadian Transportation Accident Investigation and Safety Board Act (the CTAISB Act) states that the object of the Board is to advance transportation safety by conducting independent investigations into selected transportation occurrences in order to make findings as to their causes and contributing factors. The TSB is therefore not obligated to investigate all reported occurrences.

1.3 Section 8(1)(b) of the CTAISB Act provides the Board with the authority to establish policies respecting the classes of transportation occurrences to be investigated.

2. Definitions

2.1 "Occurrence" means a transportation event as defined in the CTAISB Act.

2.2 "Reportable occurrence" means an occurrence as defined in the TSB Regulations.

2.3 “Foreign occurrence” means a transportation event in another country and subject to investigation by a foreign investigation body.

2.4 "Investigation" means all activities associated with the collection of data/ information pertaining to an occurrence (except the receipt and capture of the initial occurrence notification information), the analysis of such information (including laboratory projects and testing), the drafting, review and approval of the report, the publication of the report, as well as all communications activities intended to share information with external stakeholders.

2.5 "Report" means an official publication presenting the results of an investigation in a format prescribed by the Board and made available to the public.

2.6 "Occurrence summary" means a short summary describing the basic facts of an occurrence.

2.7 "Incident" is defined in Appendix A for each mode of transportation.

2.8 "Accident" is defined in Appendix A for each mode of transportation.

3. Policy objective

3.1 The purpose of this policy is to establish a classification structure to facilitate tracking, investigating and reporting of transportation occurrences in accordance with Section 8(1)(b) of the CTAISB Act.

3.2 This policy also sets specific criteria for investigations within each class of occurrence to

4. Policy requirements

4.1 As defined in the TSB Regulations, mandatory information shall be collected for all reportable occurrences and recorded in the mode’s transportation occurrence database.

4.2 Each occurrence reported to the TSB shall first be classified as an "accident" or an "incident" in order to facilitate statistical tracking, analysis and reporting. This classification shall be done in accordance with the definitions included in Appendix A.

4.3 Occurrences shall then be classified according to their relative importance, complexity, and potential for yielding safety lessons. This classification shall be done in accordance with the criteria and definitions included in Appendix B.

4.4 There are six classes of occurrences:

4.5 This classification is used to determine the TSB's level of effort and investment, the investigation process, the type of report or product, and the target timeline, as shown in Appendix C.

4.6 Occurrences outside Canada that the TSB investigates will be classified in the same way as occurrences in Canada. Foreign occurrences, for which the TSB provides support to another investigation body (i.e. where the TSB is not leading the investigation), will be recorded in the modal databases as class 6 occurrences.

4.7 To the extent practicable, an individual occurrence will be classified within 72 hours of receiving the initial occurrence notification.

4.8 If a measurable level of effort is made (such as deployment to the occurrence site or a laboratory project), the occurrence will generally be classified as a class 4 or above.

4.9 4.9 The classification of an occurrence can be modified (upgraded or downgraded) whenever new supporting information becomes available to justify such a change. However, once an occurrence has been classified as a class 2, 3 or 4, the Board must be briefed before it can be downgraded to a class 5.

4.10 An investigation in progress may be re-scoped if no further safety lessons emerge.

4.11 All classification decisions and the rationale for them must be documented in the investigation records.

5. Authorities

5.1 This policy is issued under the authority of the Board in accordance with sections 8(1)(b) and 8(1)(c) of the CTAISB Act. It was approved by the Board on April 25, 2018, and was last revised on February 24, 2021,Footnote 1 after consultation with the Executive Committee

5.2 This policy will be reviewed and may be updated in response to changes in government priorities or TSB strategic direction, but at least once every 5 years.

6. Role and responsibilities

6.1 Chair

The Chair is responsible for initiating the periodic review and update of this policy by the Board.

6.2 Chief operating officer

The chief operating officer is responsible for overall implementation, monitoring and oversight of this policy, as well as for seeking interpretation and guidance from the Board from time to time.

6.3 Directors of investigations and director, Operational Services

The directors of investigations (DOIs) and the director, Operational Services are responsible for communicating and implementing this policy within their respective branches. This includes ensuring that all manuals, directives, procedures, standards, and guidelines are fully compliant with this policy.

The DOIs are accountable for classification decisions.

Where appropriate, the DOIs are accountable for re-scoping further investigation work as stated in section 4.10.

6.4 Director, Communications

The director, Communications is responsible for posting this policy on the TSB website and for responding to information requests from the public.

7. References

7.1 The following acts and regulations apply:

7.2 This policy was drafted with consideration given to TSB obligations and commitments to the following international agreements and conventions:

8. Enquiries

8.1 Questions about this policy may be addressed to:

General enquiries
1-800-387-3557
1-819-994-3741
communications@bst-tsb.gc.ca

9. Appendices

Appendix A – Definitions of accident and incident for each mode

All reportable occurrences must be identified as an accident or an incident in the transportation occurrence modal database using the following definitions, which are based on the Transportation Safety Board Regulations SOR/2014-37.

A1 – Aviation accident

An aviation accident is an occurrence resulting directly from the operation of an aircraft in which

  1. a person is killed or sustains a serious injury as a result of
    1. being on board the aircraft,
    2. coming into direct contact with any part of the aircraft, including parts that have become detached from the aircraft, or
    3. being directly exposed to jet blast, rotor down wash or propeller wash;
  2. the aircraft sustains structural failure or damage that adversely affects the aircraft's structural strength, performance or flight characteristics and would normally require major repair or replacement of any affected component, except for
    1. engine failure or damage, when the damage is limited to the engine, its cowlings or accessories, or
    2. damage limited to propellers, wing tips, antennae, tires, brakes, fairings or small dents or puncture holes in the aircraft's skin; or
  3. the aircraft is missing or inaccessible.

A2 – Aviation incident

An aviation incident is an occurrence resulting directly from the operation of an aircraft having a maximum certificated take-off weight greater than 2250 kg or of an aircraft being operated under an air operator certificate issued under Part VII of the Canadian Aviation Regulations in which,

  1. an engine fails or is shut down as a precautionary measure;
  2. a power train transmission gearbox malfunction occurs;
  3. smoke is detected or a fire occurs on board;
  4. difficulties in controlling the aircraft are encountered owing to any aircraft system malfunction, weather phenomena, wake turbulence, uncontrolled vibrations or operations outside the flight envelope;
  5. the aircraft fails to remain within the intended landing or take-off area, lands with all or part of the landing gear retracted or drags a wing tip, an engine pod or any other part of the aircraft;
  6. a crew member whose duties are directly related to the safe operation of the aircraft is unable to perform their duties as a result of a physical incapacitation which poses a threat to the safety of persons, property or the environment;
  7. depressurization of the aircraft occurs that requires an emergency descent;
  8. a fuel shortage occurs that requires a diversion or requires approach and landing priority at the destination of the aircraft;
  9. the aircraft is refuelled with the incorrect type of fuel or contaminated fuel;
  10. a minor collision, a risk of collision or a loss of separation occurs;
  11. a crew member declares an emergency or indicates an emergency that requires priority handling by air traffic services or the standing by of emergency response services;
  12. a slung load is released unintentionally or as a precautionary or emergency measure from the aircraft; or
  13. any dangerous goods are released in or from the aircraft.

A3 – Marine accident

A marine accident is an occurrence resulting directly from the operation of a ship other than a pleasure craft in which

  1. a person is killed or sustains a serious injury as a result of
    1. boarding, being on board or falling overboard from the ship, or
    2. coming into direct contact with any part of the ship or its contents;
  2. the ship
    1. sinks, founders or capsizes,
    2. is involved in a collision,
    3. sustains a fire or an explosion,
    4. goes aground,
    5. sustains damage that affects its seaworthiness or renders it unfit for its purpose, or
    6. is missing or abandoned.

A4 – Marine incident

A marine incident is an occurrence resulting directly from the operation of a ship other than a pleasure craft in which

  1. a person falls overboard from the ship;
  2. a crew member whose duties are directly related to the safe operation of the ship is unable to perform their duties as a result of a physical incapacitation which poses a threat to the safety of persons, property or the environment;
  3. the ship
    1. is involved in a risk of a collision,
    2. makes unforeseen contact with the bottom without going aground,
    3. is anchored, grounded or beached to avoid an occurrence,
    4. fouls a utility cable or pipe, or an underwater pipeline,
    5. sustains a total failure of
      1. the navigation equipment if the failure poses a threat to the safety of any person, property or the environment,
      2. the main or auxiliary machinery, or
      3. the propulsion, steering, or deck machinery if the failure poses a threat to the safety of any person, property or the environment,
  4. all or part of the ship's cargo shifts or falls overboard; or
  5. there is an accidental release on board or from the ship that results in any of the events listed in subsection 8.4(2) of the Transportation of Dangerous Goods Regulations.

A5 – Pipeline accident

A pipeline accident is an occurrence resulting directly from the operation of a pipeline that results in

  1. serious injury or loss of human life;
  2. a ruptureFootnote 2;
  3. a fire, ignition or explosion that poses a threat to the safety of any person, property or the environment; or
  4. an unintended or uncontrolled release of commodity which results in a significant adverse effect on people or the environment.Footnote 3

A6 – Pipeline incident

A pipeline incident is

  1. an occurrence in which
    1. the pipeline sustains damage that affects the safe operation of the pipeline as a result of another object coming into contact with it,
    2. an unauthorized third party activity affects the structural integrity of the pipeline, or
    3. a geotechnical, hydrotechnical or environmental activity poses a threat to the safe operation of the pipeline;
  2. an occurrence resulting directly from the operation of a pipeline in which
    1. there is a fire, ignition or explosion that affects the safe operation of the pipeline,
    2. there is an unintended or uncontrolled release of hydrocarbon gas,
    3. there is an unintended or uncontrolled release of HVPFootnote 4 hydrocarbons,
    4. there is an unintended or uncontrolled release of LVPFootnote 5 hydrocarbons in excess of 1.5 m3,
    5. there is an unintended or uncontrolled release of a commodity other than hydrocarbon gas, HVP hydrocarbons or LVP hydrocarbons,
    6. there is a release of a commodity from the line pipe body,
    7. the pipeline is operated beyond design limits or any operating restrictions imposed by the Canada Energy Regulator, or
    8. the pipeline restricts the safe operation of any mode of transportation.

A7 – Railway accident

A railway accident means an occurrence resulting directly from the operation of rolling stock in which

  1. a person is killed or sustains a serious injury as a result of
    1. getting on or off or being on board the rolling stock, or
    2. coming into direct contact with any part of the rolling stock or its contents;
  2. the rolling stock or its contents
    1. are involved in a collision and/or a derailment resulting in damages to rolling stock and/or track infrastructure,
    2. sustain damage that affects the safe operation of the rolling stock,
    3. cause or sustain a fire or explosion,
    4. cause damage to the railway that poses a threat to the safe passage of rolling stock or to the safety of any person, property or the environment; or
  3. there is an accidental release on board or from rolling stock that results in any of the events listed in subsection 8.4(2)of the Transportation of Dangerous Goods Regulations.

A8 – Railway incident

A railway incident means an occurrence resulting directly from the operation of rolling stock in which

  1. the rolling stock is involved in a minor collision and/or minor derailment (1 or 2 cars) resulting in no damages;
  2. a risk of collision occurs between rolling stock;
  3. an unprotected main track switch or subdivision track switch is left in an abnormal position;
  4. a railway signal displays a less restrictive indication than that required for the intended movement of rolling stock;
  5. rolling stock occupies a main track or subdivision track, or track work takes place, in contravention of the Rules or any regulations made under the Railway Safety Act;
  6. rolling stock passes a signal indicating stop in contravention of the Rules or any regulations made under the Railway Safety Act;
  7. there is an unplanned and uncontrolled movement of rolling stock; or
  8. a crew member whose duties are directly related to the safe operation of the rolling stock is unable to perform their duties as a result of a physical incapacitation which poses a threat to the safety of persons, property or the environment.

Appendix B – Classifying occurrences

In some cases, a deployment may be required to evaluate physical evidence, interview personnel or witnesses, review documentation, etc., before finalizing a classification decision.

B1 – Factors to consider in deciding to deploy

Directors of investigations and their delegates should consider the following factors in their decision to deploy:

B2 – Key factors to consider when classifying an occurrence

The following factors must be considered when classifying an occurrence:

Most of these factors are self-explanatory. A detailed description of some factors is provided below.

Obligations and commitments

Canada is signatory to several international agreements pertaining to the conduct of investigations. The TSB is also party to several agreements for the provision of assistance to particular nations or provinces. The TSB must ensure such obligations and commitments are met.

Canadian interests in foreign occurrences

Sometimes occurrences outside Canada involve Canadian-manufactured transportation products, Canadian carriers, Canadian crews, or large numbers of Canadian citizens travelling with foreign carriers. The TSB must ensure that foreign occurrences in which Canadian products, services, or citizens are involved are appropriately investigated and that Canadian interests are adequately represented in these investigations.

Past TSB experience

In its investigations, the TSB has identified safety issues that have not been resolved over time, has published safety concerns, and noted emerging issues of interest. The TSB Watchlist, particularly, identifies the key safety issues posing the greatest risks to the transportation system.

New occurrences that are considered likely to involve risks similar to those found in previous investigations should be investigated in order to collect information that could strengthen the case for safety action.

Similarly, occurrences with safety issues that are related to Board concerns or that are among the emerging issues of interest to the TSB should be investigated in order to collect information that could contribute to the analysis of these issues and lead to new findings and recommendations.

Risk assessment

The following questions are used in the occurrence classification to assess the probability of adverse consequences arising in similar occurrences in the future:

In assessing the severity of the consequences of the occurrence, consideration is given to  the following:

Sometimes, even if there is little doubt that an unsafe condition with unacceptable risk exists, the potential for further practical safety action is limited. Consequently, an assessment will be made not only of the risks but of the potential for discovering new and meaningful  safety lessons and for safety action being taken in a reasonable time in response.

To determine the value of the safety lessons that an investigation is likely to yield, the following questions should be considered:

B3 – Classes of occurrences

Class 1 occurrence

A class 1 occurrence is a series of occurrences with common characteristics that have formed a pattern over a period of time. This pattern is made of one or more significant safety risks previously identified by the TSB or organizations in other jurisdictions in the course of their investigations, or of an issue of interest that has emerged from statistical analysis.

Class 2 occurrence

A class 2 occurrence has significant consequences that attract a high level of public interest across Canada or internationally. A large number of people are affected, some of whom may be fatally or seriously injured. There may be a large release of dangerous goods. There is significant damage to property and/or the environment. There is a high public expectation that the TSB will investigate. There is a high likelihood of identifying new safety lessons and of advancing transportation safety by reducing risks to persons, property, or the environment. A complex and exhaustive investigation is required.

Class 3 occurrence

A class 3 occurrence may have significant consequences that attract a high level of public interest. It may involve multiple fatalities and/or serious injuries. There may be a medium-sized release of dangerous goods. There is moderate to significant damage to property and/or the environment. There are public expectations that the TSB will investigate. It is quite likely that new safety lessons will be identified and that transportation safety will be advanced by reducing risks to persons, property, or the environment. A detailed investigation is required.

Class 4 occurrence

A class 4 occurrence may have some important consequences. It may involve fatalities or serious injuries. There may be a small release of dangerous goods. There is moderate to minor damage to property and/or the environment. The occurrence attracts public interest within the immediate region or province/territory. The likelihood of identifying new safety lessons and of advancing transportation safety by reducing risks to persons, property, or the environment is low.

Class 5 occurrence

A class 5 occurrence has little likelihood of identifying new safety lessons that will advance transportation safety. The occurrence may involve fatalities and/or serious injuries. There is little or no release of dangerous goods. There is minimal damage to property or the environment. The occurrence attracts limited public interest outside of the immediate area. The investigation is limited to data gathering and the data are recorded for statistical reporting and future analysis.

An occurrence that has been reported voluntarily and is not subject to the mandatory reporting requirements in the TSB Regulations may nonetheless be classified as a class 5 occurrence if it is of interest to the TSB.

Class 6 occurrence

A class 6 occurrence is a transportation occurrence that occurs outside of Canada and may or may not be investigated by a foreign investigation body. This includes investigations led by another country where the TSB is called upon to participate or provide assistance. The TSB is notified about these occurrences in accordance with international conventions and/or memoranda of understanding .

Appendix C – Investigation processes and products

Each class of occurrence follows a different process and results in a different product, as summarized in the table below. A short description of these processes and products follows the table.

Table 1. Classes of occurrence, showing investigation type, effort, investment, and process, type of report, and target timelines
Class Investigation type Level of effort Level of Investment Investigation process Type of report Target timeline
1 Safety issue Very high Very high Complex Detailed; long 730 days
2 Complex Very high Very high Complex Detailed; long 600 days
3 Detailed High High Medium complexity Medium length: up to 30 pages or 10 000 words in English, plus appendices 450 days
4 Limited scope Medium Medium Simple Short, without findings or recommendations: up to 6 pages or 2000 words in English 220 days
5 Data gathering Low Low Data gathering with or without deployment Data extract from modal database 60 days
6 Foreign investigation Low Low Assistance to foreign investigation No report n/a

Safety issue investigation (of a class 1 occurrence)

A safety issue investigation is a detailed study of a series of occurrences with common characteristics that have formed a pattern over a period of time. A safety issue investigation is conducted by a large team led by an investigator-in-charge. This type of investigation generally involves participants from multiple branches. A detailed work plan and methodology is developed and submitted to the Board for approval prior to the start of the investigation. Significant effort is placed on the collection, review and analysis of data from various internal and external sources. The report is lengthy and detailed. Investigation updates or interim reports may be released during the investigation. This type of investigation may include recommendations. The investigation is generally completed within 730 days.

Complex investigation (of a class 2 occurrence)

A complex investigation for a class 2 (i.e., major) occurrence is conducted by a large team and led by an investigator-in-charge. It involves multiple branches as well as groups with chairs and/or leads. It is conducted in accordance with the major occurrence procedures described in the TSB Manual of Investigation. It requires a very high level of effort and dedicated resources. Special funding may be required from the Treasury Board.

A class 3 occurrence that involves several safety issues requiring in-depth analysis and a complex investigation should be reclassified as a class 2. The investigation is conducted by a team and led by an investigator-in-charge. It involves participants from multiple branches. It is conducted in accordance with the standard investigation methodology described in the TSB Manual of Investigation, but it involves a higher level of effort and is more complex than a detailed investigation.

The investigation report is detailed and presents several safety issues. Investigation updates may be released during the investigation. There may also be group reports and numerous laboratory projects. This type of investigation frequently results in recommendations. The investigation is generally completed within 600 days.

Detailed investigation (of a class 3 occurrence)

A detailed investigation is conducted by a small team and led by an investigator-in-charge. It involves participants from multiple branches. It is conducted in accordance with the standard investigation methodology described in the TSB Manual of Investigation. It requires a high level of effort and is of medium complexity.

The report is of medium length and presents a small number of safety issues; it has up to 30 pages or approximately 10 000 words in English, plus appendices. Investigation updates may be released during the investigation. This type of investigation may result in recommendations. The investigation is generally completed within 450 days.

Limited-scope investigation (of a class 4 occurrence)

A limited-scope investigation is conducted by an investigator-in-charge with some support from other investigators. It requires a medium level of effort and is of low complexity.

The report is short (up to 6 pages or approximately 2000 words in English) and is mostly factual; it may contain analysis that is aligned to the limited scope of the investigation, but it does not include findings or recommendations. This type of investigation is generally completed within 220 days.

Data-gathering investigation (of a class 5 occurrence)

The investigation of a class 5 occurrence is limited to data collection. There is generally no deployment to the occurrence site and no laboratory or human factors work is done for it. The data collected is entered into the modal database and an extract of the database is published. It requires a low level of effort and is of low complexity. The investigation is generally completed within 60 days.

No investigation report is produced for a data-gathering investigation. In situations where there is a deployment, an investigation summary, which includes the rationale for classifying it as a data-gathering investigation, is provided to the Board. The investigation summary may be made available to the public in the language in which it was written, upon request, once the investigation is closed.

Foreign investigation (of a class 6 occurrence)

The TSB is not the lead investigation body on a class 6 occurrence. However, when assistance is requested by a foreign investigation body, the TSB may undertake some activities in support of the foreign investigation. There is generally no deployment to the occurrence site. The level of effort is generally low, but it can vary considerably depending upon the extent of the assistance provided to the foreign investigation body. There is no TSB investigation report. When an investigation report is produced, it is prepared and published by the foreign investigation body .