Lower Deck to Tobin Bridge
Tales of the Old Central Artery
Here's another "shortcut" on the old Central Artery that could save time during off-hours. If a driver felt tremendously lucky, this route could be attempted during mid-day.
Back in the 1980s, there was no connectivity from Interstate 93 south to the Tobin Bridge (Route 1 north). If you were driving south on 93, the primary ways to Route 1 were: (a) 128/95 north at Woburn, (b) Route 16 to Revere from Medford, or (c) Route 99 to Route 16 from Somerville.
A risky decision would be to stay on 93 south to the lower deck, and then end up on the Central Artery. On the artery, you could exit at the Callahan Tunnel, take a u-turn left under the artery, and then head north back on the artery to the Tobin Bridge.
A driver had to decide in Somerville whether to stay on 93 or exit at Sullivan Square (to Route 99). Traffic could be traveling at 55 mph at this intersection, but once under the deck be traveling at 5 or 10 mph. If you decided to stay on 93, and then were lucky enough to make it to the artery without stopping, the Callahan Tunnel off-ramp was usually backed up. An infamous blinking red light stood at the bottom of this ramp, which yielded the right-of-way to high volumes of traffic from North Street, destined mostly for the Callahan Tunnel.
The Big Dig System, aka The Sponge, has paid for itself with increased productivity and reduced air pollution; all $14 billion dollars' worth.