Complex sentence: The overpass that was built at the time, which allows pedestrians to cross over subway tracks to reach the beach from busy Bennington Street, had begun to deteriorate in the 1990s and was replaced by a new structure.
Split into simpler sentences: The overpass that was built at the time allowed pedestrians to cross over subway tracks to reach the beach from the busy Bennington Street. It had begun to deteriorate in the 1990s and was replaced by a new structure.