Accident Hazard Safety Constraint Table is where you define the Accidents and Losses that you want the system to prevent, and identify hazards – system state or set of conditions that will lead to a loss and the safety constraints.

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Create an Accident Hazard Safety Constraint Table

Go to [Diagram] – [STAMP/STPA] – [Accident Hazard Safety Constraint Table].
Identify Losses in STPA analysis

Or
1. Go to [File] – [New]
2. Select [STPA Procedure] tab and double-click [Identify Accident, Hazard, Safety Constraint]
Identify Losses in STPA analysis

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Add Accidents

To add an accident, right-click on a the table and click [Add Accident].
Add accidents and losses in STPA analysis

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Add Hazards


After an Accident is created, you can enter the hazard that could lead to the accident by right-clicking on the [Hazard] field and click [Add Hazard].
Identify Hazards in STPA analysis

Each hazard could lead to one or more accidents. In that case, you can choose an already existing Hazard from the drop-down list from [Add Existing Hazard] menu to another accident to multiple accidents.
Choose an existing Hazard

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Add Safety Constraints


When an accident and its hazard are defined, you can add the safety constraint.
Right-clicking on the [Safety Constraint] field and click [Add Safety Constraint].
Identify Safety Constraint in STPA analysis

A single safety constraint could be related to one or more hazards. In that case, you can choose an already existing safety constraint to multiple Hazards from [Add Existing Safety Constraint] and choose one from the drop-down list.
Add existing Safety Constraints

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Disable automatic ID creation

When you add Accidents, Hazards and Safety Constraints, Astah automatically gives ID starting from A1, A2, A3…for Accidents and H1, H2, H3…for Hazards…etc.

No ID for STPA models

You can directly edit it by double-clicking the ID. If you do not wish to have Astah to allocate the ID,

  1. Go to [Tools] – [System Properties]
  2. A [System Properties] window appears. Select [Other] under [STAMP/STPA]
  3. Remove the tick off [Automatically Assign IDs] option and click [Apply] – [OK].
    Hide ID for STPA models

    Please be noted that this change will stop automatically creating ID for all the other definitions such as Preconditions and Countermeasures.