HERE’S WHO will see their reputation suffer if Maryland’s $5.8 billion Purple Line project, which would connect close-in suburbs just north of the District of Columbia, collapses mid-construction, as now seems possible: everyone involved.

The light-rail Purple Line — one of the country’s most ambitious transit projects, decades in the planning — would run 16 miles in a squiggling arc, its 21 stations connecting neighborhoods, employment hubs and spokes of Metro’s subway lines in Montgomery and Prince George’s counties. It would be a boon to commuters and to older communities inside the Beltway that have not shared in the region’s exploding prosperity.

Despite those clear benefits, it has faced a barrage of existential threats — the initial recalcitrance of the Trump administration, which threatened to end funding for all transit, and Gov. Larry Hogan, a Republican who regarded the project as unaffordable; the hostility of a federal judge, who issued a specious ruling intended to kill it; and dug-in opposition by well-off suburban neighbors who feared it would diminish a beloved walking and cycling trail. The Purple Line survived all that, for one overarching reason: It makes economic and transportation sense.

The bulldozers rolled in August 2017, but the problems did not end. Litigation by neighbors and rulings by the judge, though ultimately swept aside on appeal, delayed construction by more than a year — and added nearly $200 million to the project cost, according to the contractor. Several hundred million dollars more in cost overruns and additional delays arose from sluggish land acquisition by the state, and demands for design and engineering changes by a water utility and a nearby railroad. In early April, covid-19 prompted construction crews to self-quarantine after a project inspector tested positive. Completion of the project, originally promised for 2022, could be a year or more behind schedule at this point.

Disputes over who would pay the extra cost — the state or the consortium of corporate giants building the Purple Line — triggered months of negotiations, which ultimately failed to produce a deal. On May 1, the consortium announced it would quit the job this summer, leaving an unholy mess of dug-up streets and incomplete tunnels.

That’s a disgrace that, if left unresolved, would produce a roster of losers. They include Maryland, which sunk $1 billion into the project and, to all indications, mismanaged it; the consortium, which would fail to deliver on a huge contract, thereby subverting prospects for major public-private transportation projects elsewhere; and taxpayers at the federal, state and local levels.

Carlos Hernandez, chief executive of Fluor Corp., one of three large firms behind the consortium building the project, said in a statement that the company “has a long history of completing complex and diverse projects.” That boast is sounding hollow. Maryland Transportation Secretary Greg Slater said the state remains “committed to resolving these issues and delivering the Purple Line,” but neither he nor Mr. Hogan has publicly described a path forward, which is what citizens of the state deserve.

The biggest losers would be those in the suburbs through which the Purple Line would pass, including supporters, opponents and commuters, who would be left with the upheaval of a major construction project roughly one-third completed. Their anger would be amply justified.

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