Which of the following is a safety measure when transporting passengers?

Equipping the vehicle with seatbelts is a crucial safety measure when transporting passengers because seatbelts significantly enhance passenger safety by reducing the risk of injury in the event of sudden stops or accidents. They are designed to restrain occupants in their seats and distribute the forces of a collision over the stronger parts of the body, which helps to prevent ejection from the vehicle and minimizes impact injuries. Ensuring that all passengers are wearing seatbelts is a fundamental aspect of adhering to safety regulations and promoting a safe traveling environment.

The other measures mentioned may not provide the same level of universal safety. For example, allowing only adult passengers does not ensure safety, as minors can also follow safety protocols if properly supervised. Reducing speed only around schools is suitable in those specific areas but is insufficient for ensuring safety at all times. Similarly, playing safety videos during breaks might not effectively inform passengers about safety protocols at the time they actually need to adopt them, such as before the trip begins. Hence, while other options reflect some aspects of passenger safety, equipping the vehicle with seatbelts represents a universally effective and necessary safety measure in passenger transport.