i think the latching mechanism plays an important role in the use of the harness. some harnesses can't be released when there is tension on the straps, and therefore in the case of a roll-over, cannot be undone unless you are lifted somehow (in a tight, crushed, cramped space... good luck), to relieve the tension.
Best thing to do is call the local police department and speak to someone who deals with most cases in the matter.