Developing a safety indicator to measure the safety level during design for safety

•A safety indicator (SI) proposed for safety level assessment.•SI could be used at the earliest design phases to compare design alternatives.•SI depends on the presence or absence of danger and the level of importance of hazardous conditions.

The objective of this study was to measure human safety when using a system during its design process. Safety is defined as no danger or no conditions that can create a risk. Based on this definition of safety, we established a safety indicator used at the earliest design phases based. The proposed safety indicator depends on two values indicating the presence or absence of danger and the level of importance of hazardous conditions. The power take-off drive shaft is used as a case study to illustrate and examine the proposed safety indicator.