The new rail project was started to bring traffic-plagued commuters some relief and spur economic growth. But local leaders drastically underestimated how much it would cost, with a booming construction market and utility relocation problems driving the project more than $1 billion over budget.

Now, local leaders have to come up with a solution — or consider scrapping the whole effort altogether.

It’s a familiar story on Oahu, but actually playing out nearly half a world away right now in Boston, where the price to extend that city’s Green Line on the “T” transit system has spiked from $1.3 billion to as much as $3 billion, according to official estimates.

Hawaii’s capital city is hardly alone in its rail woes, a Honolulu Star-Advertiser analysis shows. Several mainland U.S. cities — Boston, New York, Baltimore and Los Angeles — have all similarly struggled in recent years to keep up with their rail projects’ soaring costs.

“Every major complex transportation project sees cost increases,” Therese McMillan, former acting head of the Federal Transit Administration, said during a visit to Honolulu last month.

“From its concept, through the environmental work that needs to be done, through the design and engineering to construction, all of that brings progressively more information,” said McMillan, who’s now chief planning officer for the Los Angeles County Metropolitan Transportation Authority. “That very often results in cost adjustments.”

Those four cities have faced the same choices as Honolulu does now, and they’ve chosen different paths forward.

Boston-area transit officials aim to keep the Green Line extension project going by scaling back its design and securing more local funding. New York has already spent billions of dollars on a new tunnel taking shape under Manhattan and has pledged to keep digging despite the considerable increase. The Los Angeles area’s transit agency aims to cover cost increases to dig its own new downtown tunnel with dedicated sales tax sources, officials there say.

The Baltimore area, meanwhile, saw its long-awaited light rail project canceled last summer due to the rising costs.

All of these places had to consider the hundreds of millions of dollars in federal funding they stood to lose if they canceled their rail project or scaled down its scope too severely. Honolulu rail faces a budget deficit of $1.5 billion, based on the latest official estimates. The city could lose $1.55 billion in federal funding if it cancels the project or reduces its scope too severely.

Green Line Extension

The Boston area has long looked to extend the “T” system’s Green Line northwest into the cities of Somerville and Medford, with a goal of putting thousands more residents in those crowded communities within walking distance of a rail station. In recent years officials developed a project to extend the line by 4.5 miles and six stations.

“This will have a huge impact on our environment, our social fabric and on our economy as a region,” Somerville Mayor Joseph Curtatone told the Boston Globe in 2013.

However, in August 2015 the Massachusetts Department of Transportation, or MassDOT, announced the costs might surge as much as $1 billion over budget.

Among “possible” reasons for the hikes, MassDOT cited a “hot regional construction market compared to earlier recessionary pricing” and “increased utility conflicts and necessary relocations” — the same factors that Honolulu officials have pointed to for Oahu’s skyrocketing rail prices. On the island, costs have risen from $5.26 billion to at least $8.3 billion in the past two years.

The Green Line extension’s costs rose as it became more fully designed, with “updated geotechnical information,” according to a MassDOT Aug. 24 report. In Honolulu, officials recently pointed to the need for deeper ground shafts in the dense urban core as a reason for schedule delays (and added cost).

Additionally, MassDOT said that the “original estimate could have been too low.” In December, Boston-area officials halted the extension’s building contracts, according to media reports.

In May, project consultants suggested scaling back Green Line station features, including escalators, elevators and toilets. They also suggested trimming a train maintenance facility to almost half the size of its original design and to keep existing bridges along the line instead of building several new ones. Those and other moves, they said, should rein in the total cost to around $2.3 billion.

As for Oahu’s rail stations, “Everything they did in Boston, we’ve done,” Honolulu Authority for Rapid Transportation spokesman Bill Brennan said in an email Thursday. He provided a list of 105 cost-reduction items to the stations that HART gave the City Council last year.

“There’s not much savings to be had on the guideway,” Brennan added.

Boston-area transit leaders submitted the new designs to the FTA this summer for review. Honolulu and Boston-area officials are simultaneously trying to draft new, workable financial plans for their projects, records show.

In Massachusetts, transportation planners approved shifting $152 million in federal highway dollars to the Green Line extension, and the Cambridge City Council might commit $25 million to the project, according to MassDOT. Similarly, some Honolulu elected leaders say more stakeholders need to put “skin in the game” to help cover rail’s ballooning costs.

Baltimore Red Line

On June 25, 2015, as Hawaii Gov. David Ige neared his eventual decision to approve an extension of Oahu’s rail tax to help keep construction going, Maryland’s governor went in a much different direction.

“Our administration is not opposed to public transportation, but we are opposed to wasteful boondoggles,” Gov. Larry Hogan declared at a news conference that day. “I can confirm today that the Red Line as currently designed is not going to be built.”

Baltimore’s proposed Red Line, a 14-mile, 19-station light rail system, would have provided what some in the community there saw as a much-needed east-west transit line traversing Baltimore County and Baltimore city. The project would have helped relieve street congestion and serve “major employment locations,” according to an FTA report.

“It went through a variety of neighborhoods, but on the west side it went through neighborhoods where the highest percentage are spending 45 minutes or more commuting,” said Brian O’Malley, president and CEO of the Central Maryland Transportation Alliance, a coalition of civic and business groups that supported the Red Line.

However, between 2012 and 2014 the Red Line’s costs climbed by an estimated $423 million. By the end of 2014, its estimated price tag was just shy of $3 billion. The FTA had agreed to cover $900 million of the cost. Nonetheless, Hogan opted to cancel and forfeit those dollars.

“I’ve made it very clear that building, maintaining and fixing Maryland’s roads and bridges is our top transportation priority,” he said at the 2015 news conference. (Hogan’s office did not respond to a request for comment.)

The move, according to the Baltimore Sun, freed up hundreds of millions of dollars for Hogan to shift to road and highway projects across the state — outside of the Baltimore area.

State transit officials are still moving forward with new bus routes to better serve commuters under a system called BaltimoreLink. O’Malley said the bus routes are a step in the right direction, but they’re not enough. They don’t replace what the Red Line would have done, he said.

“We need to do both,” he said. “We support the bus reform. But we are not satisfied.”

He added that it will be “very difficult” to try to restart the Red Line project and persuade the federal agency to sign another funding deal. Construction costs would be more expensive than they are now, he said.

Long Island Rail Road East Side Access

In New York, the effort to build a 3.5-mile commuter rail extension into Manhattan’s Grand Central Terminal has seen numerous delays and multibillion-dollar cost increases. Nonetheless, local transit officials continue to build the massive infrastructure project.

It aims to free some 50,000 or so daily riders who use the Long Island Rail Road from having to “double back” to Manhattan’s east side from Penn Station, according to the FTA.

The East Side Access was supposed to be finished in 2009 at a cost of $4.3 billion, according to a January 2014 New York Daily News report. In 2006, the FTA signed a funding agreement with New York’s Metropolitan Transportation Authority that put the cost at $7.38 billion.

After that, “major tunneling construction and cavern excavation has progressed slower than expected in Manhattan,” an FTA report stated.

Currently, MTA officials put the project at $10.17 billion. Some $6.38 billion has been spent on the effort since July, according to MTA.

The agency says it has $2.57 billion set aside in its 2015-2019 capital program to keep building, and that it expects to provide the rest of the dollars needed in its next capital program.

LA Metro Regional Connector

Los Angeles County’s 1.9-mile, three-station underground project will link three light rail lines as they converge in downtown LA. For a sprawling West Coast city that’s long been known for its car-travel culture, officials say that the connector is an effort to make rail travel easier. Currently, passengers have to make extra transfers to hop between those three lines, according to an FTA report.

In 2013, FTA officials listed the cost of the connector at $1.366 billion. More recently, officials have estimated it will cost $1.55 billion. In a November report, the LA County Metropolitan Transportation Authority board blamed much of the issue on unforeseen utility relocation problems.

“That slowed the whole process down and increased the budget,” LA Metro spokesman Rick Jager said Friday. “This was unfortunate because we ran into things that were uncharted down there, or were so old and deteriorated that we had to rebuild them.”

Similarly, in Honolulu, crews have dug at least 22 so-called “potholes” along the last 5 miles of the rail line through town to verify that utilities are located as drawn in the plans. Only three of those holes showed utilities in their proper places, local officials say.

In LA, officials plan to use local 0.5-cent sales tax sources set aside for transit to make up the budget gap, Jager said.