Yourself, your passengers, and other road users
The driver is responsible for the condition of the car and the safety of passengers. It it is not safe to drive, don't.
The third officer in the Merchant Marines is responsible for the safety of the ship and crew. A Third Officer is licensed to be a commander of the ship should something happen to the captain, first officer, and second officer.
You are responsible for your personal safety.
The nurse, the nurse is licensed and overall is the person responsible for any patient care provided. So even if a nurse aid makes a mistake and compromises patient safety it falls onto the nurse.
This varies a great deal depending on the country or territory you are in. For example, in the USA a learner driver must be accompanied by an adult licensed driver who is at least 21 years of age, and that licensed driver must be in the seat next to the driver at all times. As this is a legal and safety matter, it's important to check with your licensing authority before you take to the road.
A collateral duty safety officer is responsible for recognizing and reporting hazards. They are responsible for the safety of workers.
There is no minimum age for a passenger, but the driver is responsible for the safety of the rider.
The Swiss Guard is responsible for the pope's safety.
The Swiss Guard is responsible for the pope's safety.
The teacher, instructor, or other person responsible for organizing the learning environment is responsible for the safety of that environment.
The Swiss Guard is responsible for the pope's safety.
The people responsible for fire arms safety are the people who are handling the fire arms.