Is it illegal for an adult to ride in the back of an SUV?

In most places, it is not illegal for an adult to ride in the back of an SUV, as long as they are using a seatbelt. However, laws can vary by state or country regarding seatbelt use and passenger safety requirements, so it's essential to check local regulations. Additionally, safety recommendations suggest that all passengers should ride in designated seating areas with seatbelts for their protection.