This is a precarious juncture for the Honolulu Authority for Rapid Transportation — which, for everyone who has watched every twist and turn in the HART saga of navigating the construction of the rail project, is familiar territory.

First, an acknowledgement of the progress rail has made, problems notwithstanding: If the Federal Transit Administration (FTA) signs off on the slightly shortened route, the guideway is 3 miles from completion. Approval of the revised route, part of the “recovery plan” for financing the budget-busting public works project, is needed to get the remaining $744 million in federal subsidies that are promised.

Further, the system is in the midst of a rigorous, 90-day trial-run phase in which any bugs can be worked out before responsibility for operations is turned over to the city Department of Transportation Services. The city still has to show it’s ready to take over, but approaching that milepost is significant.

Of course, there are also many reasons why this is a huge hold-your-breath moment. Among the unknowns making the average observer understandably nervous is the realization that cracks discovered in guideway pillars in 2018 have grown larger and could be a bigger cause for concern. This won’t be clear until the structural engineers studying the issue present their findings, but that verdict should be just around the corner.

And work is just starting on the most challenging stretch of the alignment, on the narrow and congested Dillingham Boulevard corridor. More surprises could lie just beneath the pavement there.

The biggest nail-biter may be that the FTA has not yet approved HART’s revised proposal for $9.8 billion in construction costs; the route, originally connecting East Kapolei with Ala Moana Center, now would end almost 1-1/2 miles short at Halekauwila and South streets, the Civic Center stop.

This is not evidently too worrisome, though, to HART Chief Executive Officer Lori Kahikina, who said she has seen no real signal from FTA that any of this is a deal-breaker. In response to an email inquiry from the Honolulu Star-Advertiser editorial board, Kahikina said HART is “working hand in hand with FTA, meeting weekly, to keep the process moving toward approval of the plan.

“FTA is on board with the proposed truncated scope of the system, and I’m confident we’ll come to an agreement soon on any outstanding issues they may have,” she said. As a basis for the confidence, she added that the federal agency has recommended that HART begin drafting an amended agreement, which HART staff is now working on.

Even so, it was probably a good idea that Colleen Hanabusa, the former congresswoman now in her second stint chairing the HART board, has written to the FTA in defense of the recovery plan. The concern there was that Hill International, the consultant overseeing rail on behalf of the FTA, was not aligned on details of the cost and the amount needed for contingency funds.

Hanabusa said in a phone interview that she wanted the new FTA administrator, Nuria Fernandez, to have a full understanding of Hawaii’s unique general excise tax and its tourist tax, both of them key sources of revenue for the project. That revenue picture, she said, is relatively bright, with Hawaii’s economic health as its foundation.

The rail project, with transit-oriented development potentially revitalizing neighborhoods such as Kapalama, still promises to be an asset to Honolulu commuters and businesses. If HART works to manage the traffic disruptions, and the city steps up to be ready for operations, it will be worth the sacrifice.

There is so much to do, and no time to lose.