dual gauge
...dual gauge railway generally consists of three rails, rather than the standard two rails?
...<b id="mw1A"><a href="./Dual_gauge" id="mw1Q" rel="mw:WikiLink" title="Dual gauge">dual gauge</a></b> railway generally consists of three <a class="mw-redirect" href="./Rail_tracks" id="mw1g" rel="mw:WikiLink" title="Rail tracks">rails</a>, rather than the standard two rails?