Complex sentence: A new signal box at Yallourn marshalling yard was opened in December 1953, allowing two way operation on the new line, the old line falling into disuse but not removed until March 1957 when the SECV begun to expand the Yallourn open cut mine across the alignment.
Split into simpler sentences: A new signal box at Yallourn marshalling yard was opened in December 1953, allowing two-way operation on the new line. The old line fell into disuse but was not removed until March 1957, when the SECV began to expand the Yallourn open cut mine across the alignment.