A Thales/Vortok railway track <a rel="nofollow" class="external text" href="http://www.vortok.com/signalling/track-mounting-systems-accessories/anti-trip-device">anti-trip device</a> containing a Vortok <a rel="nofollow" class="external text" href="http://www.vortok.com/signalling/track-mounting-systems-accessories/balise-mounting-system-transponder-mounting-system">balise or transponder</a>.  It's mounted on a concrete railway sleeper (the stone like object running vertically through the picture) and prevents track workers tripping over and damaging the transponder.  Select the <a rel="nofollow" class="external text" href="http://www.vortok.com/signalling/track-mounting-systems-accessories/balise-mounting-system-transponder-mounting-system">photos tab on the balise/transponder page</a> to see the transponder shaped box.
<a href="//commons.wikimedia.org/wiki/User:GT1976" title="User:GT1976">GT1976</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>