It doesn't appear that seat belts were in use. I would guess that, considering the road conditions, the car was going too fast and slid through the intersection in front of the truck who T boned the car and dragged it a ways. The passenger in the rear seat didn't leave the car until rescue workers opened the door. The passengers probably died from the impact rather than from being crushed. There would be more blood from crushing injuries. I don't think any kind of protection would have saved them because of the high velocity of the truck. I don't think the driver of truck even had time to hit the brakes.