In the standard 'Incident' rule set with automations you'll notice that you can't target specific types of people involved. This is because technically "Incident Participants" are separate records that are related to the incident.
To account for this need you can set off automations specifically based on people involved, which allows for far greater control over your automations in regards to those relationships.
Let's use an example to illustrate this: Let's say you wanted somebody to be notified when a "Person Affected" is added and reported as injured (based on what you consider to be an injury). BUT you only want to be notified once that incident has been submitted to "Investigation".
To do this:
Go to Settings > Automations.
Click [+Add] and select from the drop list: "Incident participant"
Apply the following rule set:
So this rule set states that this trigger will ONLY fire when the
workflow step is equal to "Investigation" AND
The incident participant role is equal to "Person Affected" AND
The Incident classification is equal to "Medically Treated Injury" OR "Lost Time Injury".
Since this rule set treats every Incident Participant differently, it will fire for every incident participant where those rules are met. So, if you have three people involved but only two of them meet those criteria, then this rule will fire twice.