As PB scrambled to develop design documents for Contracts 3 and 4, NJDOT began communicating with other transportation agencies on a mitigation plan. Starting early in 2013 and continuing for 15 months, "we made up to 80 presentations to major corporations in Jersey and held more than 100 stakeholder meetings," says Dave Lambert, the state's transportation engineer. "We spoke to trucking associations, first responders, the port, the airport."

NJ Transit agreed to run extra trains, buses and ferries. With $20 million from NJDOT, the turnpike authority transformed one shoulder into a managed lane. Hudson County pushed court arrival times out to 10 a.m., and firms agreed to implement flexible work schedules.

Hammer estimates traffic mitigation may make up about 5% of the project cost. "Some things can be cut eventually if they aren't needed," he adds. DeJohn says tabletop exercises, a half-dozen task forces and extra incident management and monitoring signs have been installed, and monitoring is constant. "Every day we have a debriefing on what went right and what went wrong," he notes.

Three weeks in, no major mishaps have occurred, but Sam Schwartz, former New York City traffic commissioner and a project traffic adviser, says officials have to stay vigilant and ready to reassess. "There's no getting around the fact we're losing a major artery," he says. "And we can't clog too many of the other arteries. We want to avoid a heart attack."