Would an expanded East-West rail system put the state on path to more housing affordability?

Leaders at A Better City, a nonprofit focused on growth under the lens of equity, sustainability, and improved transit, contend that the key to easing the pressure on Greater Boston and stemming its rising prices is better connections between Central and Western Massachusetts and the urban core of the eastern part of the state.

There may be no better time than the present, as there is a rail-friendly administration in the White House and funding available from the passage of the $1.2 trillion Infrastructure Investment and Jobs Act last year.

But Rome wasn’t built in a day, nor are expanded passenger rail lines. Experts and even the advocates pushing for an array of rail improvements across the state caution that it is crucial that the infrastructure push doesn’t end up elbowing out those in need of an affordable place to live.

“Unfortunately, some of the research suggests that when you do transit-oriented development, new transit investments, expansions, or enhancements, sometimes you increase the cost of housing,” said Richard Dimino, president and CEO of A Better City.

Soaring rents and home prices accompanied each of Boston’s most recent transit expansions. The Silver Line expansion through the Seaport was followed by a boom in glassy condo and apartment towers.

Somerville, once anointed with the nickname “Slummerville” for its less-than-glamorous reputation relative to neighboring Boston and Cambridge, shed that moniker in recent years as it got hitched to the Orange Line with the Assembly Station, as well as the more recent Green Line Extension, which sent rents soaring before stations even opened.

But future transit expansion doesn’t have to be that way, experts said.

A regional rail network would encompass a greater geographic stretch than recent improvements and expansions to the MBTA subway and light-rail network. It could benefit areas beyond Route 128 that are less resistant to density than some of Boston’s inner suburbs — and that want a bigger piece of an economic pie that disproportionately benefits the eastern part of the state. Instead, it would run enhanced train service to parts of the state that have felt shut off from the economic boom of the east — and give these regions a crucial role in solving a growing problem in Boston.

Boston leaders have frequently accused the surrounding suburbs of not doing enough to generate more housing stock to meet the demand. A Brookings Institution study found that restrictive zoning in the suburbs played a key part in how home prices in Greater Boston shot up 53 percent between 2009 and 2020.

“East-West rail should be thought of as one piece of a modernized regional rail network, and regional rail ought to be thought of as much as a housing and economic development strategy as a transportation strategy,” said Bob Yaro, president of the North Atlantic Rail Alliance, an organization of private and public sector leaders pushing for significant expansion and modernization of passenger rail service in the Northeast.

The organization’s Massachusetts passenger rail wish list includes evolving the commuter rail to a regional network with electrified lines and expanded service and developing East-West rail between Boston and Springfield and potentially all the way to Pittsfield.

East-West rail is one component — expected to be managed by Amtrak — while the MBTA would tackle the regional network, which encompasses the existing commuter rail system. The MBTA’s website outlines six rail vision alternatives that include measures like train service every 15 minutes to “key stations” in dense areas outside central Boston, future expansions like connecting Kendall Square with a future West Station in Allston, and electrifying various lines to operate more like urban rail service.

“If the services are really fast and frequent, reliable, and well-priced, it means that Central and Western Massachusetts get pulled into the Greater Boston commuter housing market, labor force, and labor market,” Yaro said.

But advocates also say it is crucial that the MBTA not repeat its mistakes.

Critics have dubbed the Silver Line bus system the “Silver Lie,” because its sporadic service doesn’t come close to the frequency of the former elevated Orange Line that connected Nubian Square and other parts of Roxbury with downtown Boston.

The MBTA did not respond to the Globe’s multiple attempts for a comment.

Even an East-West rail at its peak wouldn’t likely achieve the trip frequency seen on international regional rail networks. The plan is to scale up to five trips a day to Springfield.

Riders would have to stick to Worcester and, most likely, points within the Route 128 network to find the kind of trip frequency anywhere close to Paris’s RER trains or S-Bahn systems in Germany.

“Usually, it’s a way of pushing affordability to areas where the real estate developers are not very interested in developing,” Fábio Duarte, a principal research scientist at the MIT Senseable City Lab, said of the efforts to promote rail connectivity as an affordable housing solution. “It’s kind of a smoke curtain to say: ‘Yeah, we need this land. It’s valued at a lot [of money]. Let’s push these people out.’”

Indeed, rail service to outlying areas doesn’t ensure affordability. The Amtrak Downeaster line to Maine isn’t exactly home to stable prices: Brunswick’s housing prices have increased nearly 25 percent in the past year, while Portland — the former end of the train line — saw a home price increase of just over 21 percent, according to Zillow.

Rather than promote train service to points west as the silver bullet to affordable housing, Duarte said, city leaders should double down on efforts to boost inclusionary -development requirements on market-rate developers.

The Boston Planning & Development Agency typically requires 13 percent of an apartment or condo development’s units be set aside as income-restricted. But it isn’t unheard of to see inclusionary development rates soar as high as 30 percent in cities like Sao Paulo, Duarte said. The city even established Special Zones of Social Interest, or ZEIS, where 40 percent of the land was reserved for affordable housing, 40 percent was market-rate, and 20 percent went to other uses.

In Boston, developers balked at earlier pushes for higher inclusionary development requirements, but Duarte isn’t convinced they would ditch the city if they were told to build more.

“Everywhere they say, ‘Oh, but then if you increase the threshold to 20 percent, then they will not come,’” he added. “Well, let’s see.”

Even Dimino, one of the biggest advocates of enhanced rail service, acknowledges that infrastructure improvements bring some degree of uncertainty regarding affordability.

“There’s part of me that thinks it might be important that … we start really thinking about how we can better serve transit-dependent populations,” Dimino said. “[We need to make] sure the equity issues are really being dealt with directly and that we’re also trying to restore and keep affordable housing opportunities.”