Complex sentence: On November 24,1969, the 63rd Street line commenced construction, with tunnel segments being dug westward from Queens and in both directions from Roosevelt Island; the bi-level tunnel would have the subway on the top level and LIRR trains on the lower level.
Split into simpler sentences: On November 24,1969, the 63rd Street line commenced construction, with tunnel segments being dug westward from Queens and in both directions from Roosevelt Island. The bi-level tunnel would have the subway on the top level and LIRR trains on the lower level.