A critical city audit on the Honolulu Authority for Rapid Transportation and its management of the rail project comes at a difficult juncture for the 20-mile system under construction, but it urges some worthy changes that HART would be wise to incorporate.

Amid rising costs and delays, the project has come under harsh criticism from City Council Chairman Ernie Martin, who called for top HART officials to resign — and urged Mayor Kirk Caldwell to echo that call.

The two men are likely to be rivals in the coming mayoral election, so clearly politics is threaded through the entire issue. HART Chairman Don Horner did resign last week, citing the political pressures being exerted among his frustrations.

Now comes city Auditor Edwin Young, whose report issued on Friday outlined shortcomings in fiscal oversight by HART, underscoring that its financial plan hasn’t been kept up to date and that costs projections lacked sufficient documentation needed for accurate estimates.

The increasing costs for re-engineering the power lines in the Dillingham Boulevard part of the route weren’t anticipated through proper planning, according to one example in the audit.

Young also cited HART for lacking quantitative analysis before deciding to repackage the station work into smaller packages to improve bid competition.

HART Executive Director Dan Grabauskas, who has not yielded to calls for his head, tried to stave off those pointed critiques in a news conference he called prior to the audit’s public release. The audit did not find any money misspent, Grabauskas said, and HART accounted for all funding.

Grabauskas defended other protocols disparaged by the report, including the payment of stipends for proposal preparation by prospective contractors, as accepted industry standard and countered that HART does update its financial plans in conjunction with the Federal Transit Administration.

Among the myriad other points, he asserted that repackaging the contract work paid off, saving roughly $38 million in project costs.

All of that may be true, and even within the range of best practices. But HART needs to go beyond that level if it’s to succeed with the even more challenging miles of route that lie ahead.

Some of Young’s recommendations resonate with particular strength, including proposals that the rail agency:

>> Develop a process for tracking and monitoring all costs.

>> Support its cost estimates with “consistent, reliable and sufficient information.”

>> Develop “a forecasting model to best predict escalation costs and support it with documentation.”

More-timely and accurate cost projections will undoubtedly be tough facts to reckon with during a political season when the costs of rail will be a central issue, particularly in a mayoral race in which candidates want to put distance between themselves and unpleasant truths.

However, there is a reason HART was established as a quasi-independent agency, and that is precisely to provide the separation it needs to do a professional job of planning and implementation.

That requires that officials relay the truth of what’s ahead as the rail construction moves closer to the densely urbanized parts of Honolulu, and what contingencies are planned to ease the impact on the businesses and the commuting public.

The more detailed, documented forecasting urged by Young would support the project moving in the right direction.

Pressure from the frustrated public, even calls to halt the line at Middle Street, are likely to rise as the campaign intensifies in the coming months. HART needs to reinforce the critical message that the project, properly completed to Ala Moana Center, will reshape Honolulu’s transportation system and focus development where it needs to be. Those are key elements in the city’s future planning that should not be sacrificed.

But the public also needs to know that the people in charge have a much tighter rein on the project than the audit suggests it has. HART, and its partners in the city administrative and legislative branches, surely should take the audit’s recommendations to heart. A course correction is essential to meeting Honolulu’s goals for its biggest public-works investment.