With Friday’s passage of Senate Bill 4, the Legislature provided the money it deemed necessary to close a budget shortfall and complete Honolulu’s rail transit system. But SB 4 gives state lawmakers something else — a key management role in the project.

Due to the deep mistrust between state lawmakers and Mayor Kirk Caldwell’s administration, the Legislature increased its oversight of the massively over-budget project, including reviewing invoices and putting its own non-voting members on the rail transit’s board of directors.

That doesn’t let Caldwell and company off the hook, of course. The city and the Honolulu Authority for Rapid Transportation (HART) remain primarily responsible for finishing the project. They will have to step up their game to stay within the $8.165 billion budget set by the Legislature.

Caldwell, who forcefully lobbied against SB 4, saying it didn’t provide enough money, needs to get behind the new reality and do everything he can to make it work. It won’t do for the Federal Transit Administration (FTA), with its $1.55 billion stake, to hear contradictory views coming from state and city officials while reviewing the financial recovery plan.

It’s also past time for state and city political leaders to put an end to their bitter and fruitless dueling. They need to come to a consensus on getting the job finished once and for all.

That includes Hawaii’s congressional delegation. U.S. Rep. Colleen Hanabusa and U.S. Sen. Brian Schatz, who have been in contact with the FTA, publicly supported the Legislature’s plan; it will be incumbent upon them to do everything they can to ensure the FTA supports it, too.

Caldwell and HART will have to work closely — and cooperatively — with the state to see that the project is properly managed and costs tightly controlled between now and the opening of the Ala Moana Center terminus, sometime in the next decade or so.

Toward that end, state lawmakers used SB 4 to change some of the ground rules:

>> The $2.4 billion in additional tax revenues will come not only from a three-year extension of the Oahu-only general excise tax surcharge ($1.04 billion), but also from an increase in the statewide transient accommodations tax ($1.32 billion) — essentially giving every island some “skin in the game.” The funding scheme runs through 2030.

>> SB 4 creates a mass transit special fund, controlled by the state, to collect tax revenues for the capital costs of rail. State officials will review and certify the project’s invoices before releasing money from the fund to HART.

>> The Senate president and House speaker will each appoint two non-voting, ex-officio members to HART’s board of directors.

>> The state auditor will conduct a deep-dive audit into HART’s management, as well as do annual reviews.

It’s hoped that these changes will bring some much-needed, tougher oversight and cost controls to the rail project.

To begin with, the state’s review of the project’s invoices should be done with maximum public transparency.

Further, the audit, while not the formal “forensic” independent audit rail critics have demanded, should look closely at the many contracts, subcontracts, change orders and other expenditures approved by the city and HART from the beginning. Somewhere in there should be a fuller explanation of how rail went from a $5 billion project to what some expect will become a $10 billion one.

The public deserves detailed answers, which so far it has been denied. And if the audit turns up evidence of fraud, improper charges or other malfeasance, investigations into civil or criminal liability should ensue.

None of this will assuage rail’s opponents, who don’t want the project built at all, fearing the blight of giant pillars and guideways looming over the city, costing billions to build and many millions to maintain — and for what?

There’s no denying that construction of Honolulu’s rail transit system has been more difficult and expensive than it should have been, and that some of the predictions of rail’s opponents have come to pass, especially their doubts about the cost projections.

Still, the unrelenting traffic gridlock between West and East Oahu, combined with a need to target population growth, make the rail system more than just a train.

The project is expected to drive development near the rail stations, allowing for greater density and more affordable housing as Oahu’s population expands. Without the availability of an efficient commute to town, development pressure could grow in areas where the commute is less onerous, like the Windward side — or in parts of the island that are still rural or ecologically sensitive.

Oahu is getting more and more crowded, and that includes cars. Without a practical alternative to driving, traffic all over the island — but especially to where people live, work and shop — will continue to get worse, until it becomes unbearable.