Editing Big Dig (section)

=== Mixing of traffic ===
A major reason for the all-day congestion was that the Central Artery carried north–south traffic and east–west traffic. Boston's Logan Airport lies across [[Boston Harbor]] in East Boston. Before the Big Dig, the only access to the airport from downtown was through the paired [[Callahan Tunnel|Callahan]] and [[Sumner Tunnel|Sumner]] tunnels. Traffic on the major highways from west of Boston—the Massachusetts Turnpike and [[Storrow Drive]]—mostly traveled on portions of the Central Artery to reach these tunnels. Getting between the Central Artery and the tunnels involved short diversions onto city streets, increasing local congestion.