Northbound Tunnel Opening for Boston's Big DigThe 2.4 km northbound tunnel on Interstate 93 opened to motorists on 30th March. The tunnel runs under Atlantic Avenue starting near South Station. The tunnel's completion is a major milestone for the $14.6 billion Big Dig in Boston, the largest highway construction project in US history, which has been beset by cost overruns and scheduling delays. The I-93 northbound tunnel will trim the Braintree-to-Charlestown rush-hour commute from 45 minutes to about 20. The new I-93 northbound tunnel is wired into the Integrated Project Control System, a network of 72 video cameras, traffic-flow sensors, carbon monoxide gauges, and electronic signage that allow workers at the Big Dig's South Boston control centre to monitor traffic in the tunnel and respond to accidents and emergencies. The Big Dig had its first major tunnel opening on 18th January, when the $6.5 billion Fort Point Channel Crossing, linking the Massachusetts Turnpike to the Ted Williams tunnel and Logan Airport, opened to traffic. Visit www.bigdig.com and www.masspike.com 14/03.