Bill de Blasio delivers his address Tuesday. (Andrew Burton/Getty Images)

New York City could have a ferry service connecting all of the city’s boroughs by 2017, Mayor Bill de Blasio announced Tuesday.

The idea is to create an affordable system for travelers that could also spur development in the city’s outer boroughs, de Blasio (D) said during his “State of the City” address. He said that ferry rides would cost the same as a MetroCard fare so that trips would “be as affordable to everyday New Yorkers as our subways and buses.”

“For years, the conventional wisdom has been that certain neighborhoods are doomed to isolation because of their geography,” he said, according to an advanced copy of his remarks. “We are going to change that.”

De Blasio’s address Tuesday was largely focused on his administration’s plans to improve affordable housing in the city, which he said presents “a profound challenge” to New Yorkers. The high housing costs in New York tie into the issue of income inequality, which was a centerpiece of de Blasio’s mayoral campaign in 2013.

He outlined plans to invest heavily in bringing more affordable housing and new infrastructure to the Bronx, set aside $30 million for spaces for artists to live and work, maintain 120,000 units of existing affordable housing and require major rezoning developments to include affordable housing in their plans. A legal defense fund will now provide free legal aid to tenants in rezoned neighborhoods, the vast majority of whom currently go to housing court without a lawyer, de Blasio said.

The idea of enhancing transportation to Manhattan is interesting because of the increasing number of people who commute there from the outer boroughs. The number of workers in Manhattan who traveled from these other boroughs increased between 2002 and 2009, even though the number of New York City residents overall working in Manhattan went down in the same period, according to a 2012 study from the Rudin Center for Transportation Policy and Management at New York University. This study found that three-quarters of all commutes to Manhattan involved some form of public transit.

Ferry service could be used to essentially connect people in “underutilized waterfront areas,” while also giving travelers in areas not well-served by transit an easier way to get to bus or subway lines, the New York City Economic Development Corporation said in a report that studied how other ferry services in the city had been implemented.

Looking to nearby rivers for help in alleviating congestion is not a new idea, but it has intrigued transportation planners in some areas. In Washington, there has been talk for decades of shuttling commuters on the Potomac River, something that has not materialized. A ferry service was launched in 2012 between Oakland and San Francisco, but it initially underperformed, carrying fewer passengers than planners expected (though those numbers spiked during a transit strike in 2013).

Still, the idea of looking to the rivers is only going to seem more appealing to cities in the years ahead. An expansive study released this week by the U.S. Department of Transportation — titled “Beyond Traffic” — looked at how we will get around over the next three decades. It determined that by 2045, personal vehicles will still be the primary way people get to work, but warned that offering affordable housing and transportation options would present “an increasingly important policy challenge.”