We don't know why mental rehearsal improves performance, only that it does. Making the connection I could not find any research on the effects of imagery on safety-related behavior. But given the variety of performance behaviors that have benefited from this practice, it's obviously a useful tool to prevent injury. We can mentally rehearse images to anticipate and prepare for tasks. Your imagery can activate a chain of safe operating procedures, as well as motivate action.
Motivation comes from imagining potential consequences following safe versus at-risk behavior.
Figure 1 depicts a negative consequence you might visualize to motivate use of personal protective equipment. This image also suggests the safe behavior needed to avoid injury, making it both directing and motivating. It's often more useful to create a mental picture of positive consequences resulting from your safe actions. Focusing on positive outcomes can increase your confidence in being successful, as well as increase your desire to reach your goals. It's important to be active when using imagery.