BSicon, parallel tunnel lines (straight underground track on the left, halt on the right)
<a href="//commons.wikimedia.org/wiki/User:Sardon" title="User:Sardon">Sardon</a> &amp; <a href="//commons.wikimedia.org/wiki/User:ZandDev" title="User:ZandDev">ZandDev</a>
<span class="int-own-work" lang="en">Own work</span>