A passing loop ( also called a `` passing siding '' , `` crossing loop '' , `` crossing place '' or , colloquially , `` a hole '' ) is a place on a single line railway\/tramway , often located at a station , where trains\/trams in opposing directions can pass each other . A passing loop ( also called a passing siding , crossing loop , crossing place or , colloquially , a hole ) is a place on a single line railway or tramway , often located at a station , where trains or trams in opposing directions can pass each other .