Selkirk hurdle
...that due to a lack of freight crossings of the Hudson River, trains must take a 280-mile (450 km) detour, the Selkirk hurdle, to cross into New York City from the south or west?
...that due to a lack of freight crossings of the <a href="./Hudson_River" id="mwE0s" rel="mw:WikiLink" title="Hudson River">Hudson River</a>, trains must take a 280-mile (450 km) detour,  the <b id="mwE0w"><a href="./Selkirk_hurdle" id="mwE00" rel="mw:WikiLink" title="Selkirk hurdle">Selkirk hurdle</a></b>, to cross into <a href="./New_York_City" id="mwE04" rel="mw:WikiLink" title="New York City">New York City</a> from the south or west?