Complex sentence: In 2012, work began on a new station, which includes two longer high-level platforms and an overhead pedestrian bridge, which will eventually allow direct access from the Beacon Street and Brookline Avenue overpasses through the planned Fenway Center development.
Split into simpler sentences: In 2012, work began on a new station, which includes two longer high-level platforms and an overhead pedestrian bridge. The bridge will eventually allow direct access from the Beacon Street and Brookline Avenue overpasses through the planned Fenway Center development.