Complex sentence: Being a principal gateway to Hong Kong Island from the Kowloon Peninsula, thousands of residents passed through the pier daily from 1957 until 2006, although the inauguration of the Cross Harbour Tunnel in 1972 had an impact on the flow of passengers.
Split into simpler sentences: Being a principal gateway to Hong Kong Island from the Kowloon Peninsula, thousands of residents passed through the pier daily from 1957 until 2006. However, the inauguration of the Cross Harbour Tunnel in 1972 had an impact on the flow of passengers.