Ah, here&#x27;s one from a pro-helmet resource: <a href="http:&#x2F;&#x2F;www.bhsi.org&#x2F;limits.htm" rel="nofollow">http:&#x2F;&#x2F;www.bhsi.org&#x2F;limits.htm</a><p>It indicates that helmets in the U.S. are only tested for 14 mph impacts.<p>It&#x27;s not that the helmet stops working altogether, it&#x27;s that the helmet&#x27;s protection really isn&#x27;t sufficient.  It&#x27;d be better to wear a full-face motorcycle helmet, but of course that&#x27;d be miserable on a bike.