Complex sentence: Governor John Volpe interceded in the 1950s to send the last section of the Central Artery underground, through the Dewey Square Tunnel; while traffic moved somewhat better, the other problems remained.
Split into simpler sentences: Governor John Volpe interceded in the 1950s to change the design of the last section of the Central Artery, putting it underground through the Dewey Square Tunnel. While traffic moved somewhat better, the other problems remained.