Quantitative Risk Assessment

For moderate- and high-risk problems, and when a more detailed assessment would help determine how best to lower the probability of occurrence and how to lessen the consequences, Quantitative Risk Assessment can be used to help determine:

  • what specific starting events will lead to system failure
  • how severe the consequences of the system failure are
  • how frequently these consequences occur.


In Quantitative Risk Assessment, the severity of consequences and the likelihood of occurrences resulting from a given activity in the work scope are quantitatively (e.g. the number of people injured or the dollar amount of damage done during an operational period) categorized.

Available methods include:

  • Failure Modes and Effects Analysis (FMEA): Systematic method for examining the effects of component failures on system performance and surroundings. FMEA determines which initiating events (component failures, operating conditions, external events, etc.) will lead to significant adverse consequences.
  • Fault Tree Analysis: Method for determining which initiating events lead to a system fault. Each initiating event is assigned a probability, allowing for a calculation of the system fault probability.

Regardless of the method used, the quantitative risk assessment process should include:

  • Input from SMEs, workers and management
  • Suggested controls (engineering and/or administrative) for each hazard identified