Professor Roger Jensen | Assessing Workplace Hazards Using Risk Matrices

A common tool to assess workplace hazards is the so-called risk-assessment matrix. Most often, these consist of a grid spanning across two dimensions. One dimension represents the foreseeable harm, the other represents the likelihood of it occurring. Each dimension is presented in ordered categories, and the categories are named to make each one distinct.

Industrial employers have teams to select the categories based, in part, on the category names. Historically, committees have named categories for each dimension without the benefit of scientific studies. This is a concern, because the choice of category determines the risk. Accurate values of risk support sound decisions about safety-related actions.

Roger Jensen, a Professor at Montana Technological University, worked with two students to provide a scientific basis for making risk-assessment matrices more usable and accurate. In their research, they asked students to report what various terms mean to them on a 100-point scale. Professor Jensen used the results to recommend sets of category names for each dimension.

In his paper, he also outlines a basic risk grid design, depicting it as three planes that resemble a building with three floors.

The ground floor represents the relationship between the probability that hazardous events will occur and the severity of their consequences in logarithmic units. The system safety community uses this approach for highly-hazardous industrial processes.

The next floor of the metaphorical building is based on linear scales normalized to a range from zero to ten.

The top floor is the usable risk matrix – the version that risk-assessment teams can use to assess workplace hazards.

This grid features the same area as the floor below it, but with two design adaptations that enhance its usability – one being the use of appropriate terms to name each row and column category based on Dr Jensen’s research. The second usability factor is the use of numerical risk indicators to assign different colours that highlight areas on the matrix with similar risk.

Findings from Professor Jensen’s studies offer valuable insights into the use of risk matrices for assessing workplace hazards. His design recommendations and science-based choice of terms could support the work of occupational safety & health practitioners worldwide, encouraging them to bring more science to the practice of occupational safety & health.