A rollover rarely kills with the roll. It kills with the few inches the body travels toward a roof that is coming down to meet it.
Excursion is the movement of an occupant away from the seat during a crash: forward, sideways, upward. In a rollover it is the whole game. A belt is built to hold you to the seat, but webbing has slack and stretches, and as the vehicle turns over the direction of force keeps changing, so the body loads the belt from angles it was never optimized for. The occupant moves.
At the same time, the roof. When a vehicle comes down on its pillars they can crush inward, and the survival space, the distance between the occupant's head and the structure, shrinks. Excursion and roof crush travel toward each other. The injury happens where they meet, and it lands on the head and neck, which cannot carry that load.
Pickups are exposed twice over. A higher center of gravity rolls more easily, and the federal roof-strength standard is written as a ratio of strength to the vehicle's own weight, so a heavy truck needs a proportionally stronger roof to pass, and older or lighter structures carry less margin.
The move: excursion is measurable after the fact. Load marks on the belt webbing, the D-ring, the pattern of roof deformation, the occupant contact points. That reconstruction is the difference between "she died in a rollover" and showing the jury the inches that killed her, and whether the roof or the restraint gave up first.
One caution, so it is not oversold. Not every rollover is a defect case. Sometimes the restraint did its job and the forces were simply past survival. The work is to read the vehicle and find out which.
On the federal roof-crush standard, see FMVSS 216 (49 CFR 571.216), which measures roof strength as a ratio to the vehicle's own weight. This is general information, not medical or legal advice.
