By Joseph A. Curtatone

(The opinions and views expressed in the commentaries of The Somerville Times belong solely to the authors of those commentaries and do not reflect the views or opinions of The Somerville Times, its staff or publishers)

The Green Line Extension has been the focus of discussion in recent weeks, as the state explores ways to bring down projected costs and ensure that the most important transit infrastructure project in Massachusetts today keeps moving forward. But our Commonwealth must solve even greater mobility issues if we are to ensure our economic competitiveness going forward. It’s true, the Green Line Extension is the most important project on the books because it will spur significant production of homes and jobs that the region needs, as well as help the State meet environmental goals. But it addresses just one part of the coming transportation challenge our metro region will face. Three-quarters of the world’s population will be living in city regions by 2050, according to the United Nations. We know this future is coming. We need to plan for this future by asking: How are we going to move everyone around? Cycling, walking and transit—and, yes, even a smarter approach to our use of cars—are all part of the solution. In short, we need a statewide mobility plan that encompasses all forms of travel.

Somerville should see its population grow by between 12,000 and 18,000 people by the year 2030, according to projections by the Metropolitan Area Planning Commission (MAPC). That means our community will likely have anywhere from 85,000 to 95,000 residents. If that seems like a lot of people in what is already the most densely populated city in New England, remember that during World War II, more than 105,000 people lived in these 4.1 square miles. Meanwhile, the Metro Boston region of almost 4.5 million people should grow by between 294,228 and 561,708 people by 2030. Even under the smaller “status quo” scenario—and it’s more likely to be the stronger scenario with even more people moving into the region—most of Metro Boston’s population growth will be concentrated in the inner core.

Somewhat ironically, it was car-centric planning of the past that led to population declines in Somerville and elsewhere. As we built highways at the expense of neighborhoods and removed rail and trolley service, populations shifted to the suburbs. Today we’re undoing those Eisenhower-era policies by rebuilding connections between neighborhoods and cities that allow for all forms of travel. We’re creating streets that accommodate biking and walking along with cars, and we’re expanding public transportation.

But even as we do that, we recognize that cars are still part of the mobility equation. The Big Dig was not necessarily designed to alleviate congestion on the Central Artery—it only added an additional lane in each direction—but to alleviate other congested major roads and routes. By simplifying east-to-west connections and improving flow, there would be less traffic congestion on the Pike in Boston, to and from Logan Airport, and on Storrow Drive. We have to find ways to engineer better traffic flow, create more efficient parking, and accommodate those vehicles without necessarily building new highways, while also thinking ahead to a future when self-driving cars will likely be a reality and technology will increase ride-sharing.

Building more capacity for cars and improving traffic flow alone won’t solve the problem though. Wider roads create “induced demand,” meaning that drivers quickly gravitate toward the upgraded roadway and within a year of opening, it’s usually congested again. More cars will further deteriorate our air quality and increase our contribution to climate change. That’s why expanded public transit isn’t just a desired amenity—it’s an absolutely necessity. It’s why the Green Line Extension is so important. The trains already run through our city. They need to stop here, too. Same for the neighborhoods in Dorchester, Mattapan and Hyde Park along the Fairmount line. That’s why the MBTA is building new stations along that commuter rail line and envisions diesel multiple units running along those tracks that would provide rapid transit to those neighborhoods underserved by public transit. And extending the Silver Line through East Boston to Chelsea also brings affordable public transportation to communities historically underserved by transit.

And again, public transportation is one piece of this mobility puzzle. Better walking and biking infrastructure relieves congestion too. Building the Community Path extension alongside the Green Line Extension creates a link between the Charles River paths in Boston and Cambridge, and the Minuteman Commuter Bikeway, resulting in a 48-mile continuous network of paths. The Revere portion of the Northern Strand Community Trail recently opened, bringing that path one step closer to a 7.5 mile bike and walking route from Everett through Malden, Revere and Saugus to Lynn. We need to connect that to downtown, too. And we must continue building dedicated bike lanes when possible, including protected cycle tracks like what’s coming for Beacon Street and to Commonwealth Avenue in Boston.

Ease of mobility is a critical component to a local economy. It’s part of the reason companies locate where they do—not just to avoid traffic jams, but where talent lives and can easily move around, bump into one another, collaborate and spark new ideas. Meanwhile, we know that we live in the era of the greatest wave of urbanization in the world’s history. We need to ask: How are we going to move everyone around? And the answer is: Lots of ways. We need to plan for and build a wide range of transportation systems—for public transit riders, bicyclists, walkers and car drivers—because the cities and regions that plan for that future that we know is coming are the places that will thrive and be economically competitive in the 21st century global economy.