It’s only been four years since the first concrete was poured for Honolulu’s elevated rail project, but the current reality of a project bogged down in problems and escalating costs seems worlds away from that relatively optimistic period.

As project planners have contended, there has been the “bad luck” of lawsuits and delays, but there also have been major missteps in planning, with officials slow to bring the hard truth forward.

The belated revelations about skyrocketing costs, and about the rail route conflicting with power lines, stand as the most vivid examples.

There are sure to be more hard truths to come, with new billings for change orders and new technical issues undoubtedly ahead on the most urbanized half of the alignment.

And yet, despite the public wariness, the best way to complete the route to Ala Moana as planned is with eyes wide open. Taxpayers and policymakers need all the available facts about what’s ahead, so that realistic expectations can be set and plans with the best chance of success can be forged.

The Honolulu Authority for Rapid Transportation has just signed the contract for what’s known as the airport phase of the next stretch, between Aloha Stadium and Middle Street.

The joint-venture partnership of Shimmick/Traylor/Granite will receive nearly $875 million for designing and building the 5.2-mile section, along with its four stations.

A jittery public regards this with a sense that’s far less “Here we go!” than “What can go wrong now?”

Even if the superheated mayoral campaign wasn’t raising the temperature, the taxpayer would have reason to worry. A system on which a $5.3 billion price tag had hung not long ago is now projected to cost $3 billion more than that.

Colleen Hanabusa, who chairs the HART board when she’s not running to reclaim her former seat in Congress, is less than sanguine about this contract.

The next phase itself is hundreds of millions more costly than expected at the outset of the project.

HART should persist in drilling down on contract expenditures, driving as hard a bargain as possible for the taxpayer.

But even that won’t be enough.

In an interview with Honolulu Star-Advertiser editorial staff, Hanabusa said the board is urging HART management to bring a thorough assessment of costs and the real consequences of alternatives when it presents its “recovery plan.”

That’s what officials call the revised strategy for completing the project, a plan that can meet the terms reached between the city and the Federal Transit Administration.

The FTA has reason to demand such a plan. The current local financing mechanism is a surcharge added to the general excise tax paid on Oahu. Once the pledged $1.55 billion in federal funds is added to the local tax coffers, the total yield will only be about $6.8 billion.

And if the federal government isn’t reassured by the recovery plan that the project indeed can recover, even the $1.55 billion is not assured.

The full funding grant agreement is between the FTA and the city, and the recovery plan originally had been due in August. Mayor Kirk Caldwell had asked for an extension to produce it. He got one — but only until the end of the year, well shy of the mid-2017 extension he had sought.

Neither the city officials nor HART, then, can make firm pledges in that plan of additional local funding to help bridge the gap, as the state Legislature won’t be in session.

It’s plain that more money will be needed to produce a project that can pass federal muster. Some may be available and should be sought through public-private partnerships on the remaining stations in the city center.

But if additional tax funds must be sought, decisionmakers at the city and state levels must have a full understanding of costs, and what’s at stake.

Hanabusa rightly observed that the federal government will expect the project to meet the criteria of a “minimum operating segment” defined in the funding agreement.

The parameters are set: 20 miles and 21 stations, from East Kapolei to Ala Moana.

If those elements are to change, HART needs to persuade the FTA that it won’t be sacrificing too much in the way of ridership.

Cutting out stations likely will cost more in the loss of ridership than it will yield in a lowered price tag.

The city should be especially reluctant to sacrifice the more expensive rail stops, such as the one at Pearl Highlands.

Those are the stations most useful in attracting riders (in this case, those who will drive from Central Oahu to the park-and-ride planned at Pearl Highlands).

Honolulu needs a rail system that actually will work, not a multibillion-dollar white elephant.

The city has invested too much already to plunge ahead without the clearest of reality checks on what’s needed, and what’s ahead.