It is extremely challenging to keep occupants in a car safe without wearing seat belts, which are carefully designed safety devices that can effectively reduce injuries in an accident. However, some of the following measures can improve in-car safety to a certain extent: 1. **Driving habits**: Ensure safe driving, obey traffic rules, control speed, maintain a safe distance, and avoid sudden braking and sharp turns. 2. **Use airbags**: Make sure your vehicle is equipped with and properly maintained airbags. Although airbags work best together with seat belts, they can reduce the impact of a collision to a certain extent. 3. **Vehicle safety technology**: Choose a vehicle equipped with modern safety technology, such as automatic emergency braking, lane keeping assist, blind spot monitoring, etc., which can help prevent accidents. 4. **Child safety seats**: If there are children riding, always use appropriate, certified child safety seats, and try to choose seats that are easy to install and suitable for the child's age and weight. 5. **Keep the car clean**: Make sure there are no loose items in the car, which may become dangerous flying objects in the event of a sharp turn or collision. 6. **Seat adjustment**: Adjust the seat and headrest to the correct position to provide the best support and safety. The seat back should be at a proper angle and not tilted too much. Nevertheless, the above measures can only provide safety to a certain extent and cannot replace the protection of seat belts. So the best option is to always use seat belts. It significantly reduces the risk of serious injury and death in a car accident.