a single traffic collision
... that Ireland recently experienced its highest number of fatalities in a single traffic collision?
... that Ireland recently experienced its highest number of fatalities in <b id="mwHOk"><a class="mw-redirect" href="./July_2010_R238_traffic_collision" id="mwHOo" rel="mw:WikiLink" title="July 2010 R238 traffic collision">a single traffic collision</a></b>?