&gt; I think we can tolerate about 0.5g of deceleration<p>Untrained human beings can handle minutes of linear deceleration (perpendicular to the spine) at 12 g, and at least a second at 25 g. Strapped, mind you. And the limits are higher in backwards-facing seats (eyeballs-in is ~17 g untrained) with the additional advantage that very little strapping is needed.