It will help keep your head from bobbing outside the vehicle as it rolls, preventing your death from a crushed skull. Edited to add: "partial ejection" are th

It will help keep your head from bobbing outside the vehicle as it rolls, preventing your death from a crushed skull. Edited to add: "partial ejection" are the magic google words. Here's an example: "It was found that, in standard impact tests on high containment barriers, partial ejection of the head through the side windows occurs systematically" from: https://trid.trb.org/view.aspx?id=750825 https://trid.trb.org/view.aspx?id=750825