U.S. warning sign for Slippery When Wet (former type). Newer versions picture the driver wearing a shoulder-sash seat belt per recent legislation. Compare:
<a href="//commons.wikimedia.org/wiki/File:MUTCD_W8-5.svg" title="File:MUTCD W8-5.svg">File:MUTCD_W8-5.svg</a>
<a href="//commons.wikimedia.org/w/index.php?title=User:Cramyourspam&amp;action=edit&amp;redlink=1" class="new" title="User:Cramyourspam (page does not exist)">Cramyourspam</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>