Former Gov. Ben Cayetano — challenged to produce an alternative to the elevated rail project he vows to halt if elected Honolulu’s mayor — has responded with a combination of new express bus routes, underpasses, a Nimitz Highway flyover, contra-flow lanes and other traffic adjustments he’s dubbed "Flexible Affordable Smart Transportation" (FAST).

Let’s see how that description holds up.

Because there is no clear data demonstrating the combined effectiveness of FAST’s particular array of components, the only "flexibility" in the plan appears to come from Cayetano’s willingness to change it.

"If this thing doesn’t work, then we try something else," Cayetano said.

Considering the amount of taxpayer money involved, Cayetano should have a better idea what he’s buying.

As for "affordable," there was not enough data provided in Thursday’s presentation to justify his price tag: $1.1 billion, an alluringly petite fraction of rail’s $5.26 billion projected cost.

After being questioned about this obvious omission, Cayetano’s team has said it will produce a more detailed financial plan this week. One would have expected more up front, especially since Cayetano has made cost a key issue. He and other rail opponents routinely claim that the financial plan for rail is inadequate, failing to anticipate the true costs of the project. Will his FAST team produce figures that are more precise, realistic and detailed? We’re not holding our breath.

The "smart" claim looks shaky as well. The candidate did not give an acceptably precise projection for his system’s capacity — no details on bus ridership numbers, for example — nor explained how the elements work together to lure more drivers out of their cars and into the fleet of express buses.

Cayetano is proposing to abandon a rail project that’s already under way with millions invested and millions more in the pipeline, in a city whose residents — particularly in West Oahu — are desperate for better commuting solutions. If he expects voters to choose FAST over the city’s rail plan, he owes them a proposal that’s better vetted and fleshed out than this one, one that can come close to delivering the same service.

He also owes them answers, and declining invitations to debate in two of four proposed venues is no way to fulfill that responsibility. Last week, Cayetano turned down requests for debates at Hawaii News Now and KHON, while his opponent, Kirk Caldwell, accepted all four bookings that were offered. And he shouldn’t be quibbling about the formats; among other complaints, he said he needs more time for rebuttal, but on multiple occasions in past debates, he has yielded time he was given.

While Cayetano is coy with the hard facts, city officials who are pressing ahead with the rail project are happy to supply data that poke holes in Cayetano’s FAST plan.

First, the cost: Wayne Yoshioka, director of the city Department of Transportation Services, said the Nimitz flyover — the elevated two-lane extension of the H-1 freeway viaduct meant to take eastbound traffic in the mornings and reversing direction for the afternoon rush — was studied in 2009 during the Lingle administration and was estimated then to cost at least $600 million, just by itself. That at least suggests that Cayetano’s working with out-of-date figures in arriving at the $1.1 billion figure, or simply lacks enough hard numbers altogether.

Further, last week’s presentation failed to acknowledge that a system so dependent on buses — dozens would be included for the FAST system — will add significantly to operating costs. About 70 percent of the current bus system’s operational budget is for labor, Yoshioka said, and in that area driverless train cars have the advantage over buses.

Other elements of FAST were considered in previous iterations but jettisoned.

Underpasses are proposed at select intersections on Kapiolani Boulevard, Beretania Street, Kalakaua Avenue and Ala Moana at Alakea Street to usher traffic through more smoothly. The city contemplated this idea in an earlier bus rapid transit proposal but found the projects too costly because of the need to relocate utilities, Yoshioka said.

And the devices have their own visual impact, he said: The elevated water table means one street could only tunnel down a half level while the cross street has to be elevated to go over it.

Some good ideas in Cayetano’s plan — synchronization of traffic signals, for one — are already being implemented, Yoshioka said. But they’re simply not enough to increase the carrying capacity by a factor that comes close to what rail offers: at peak, 8,000 people can move through the system each hour. An optimized bus system like FAST? According to Yoshioka’s figures, capacity is about one-eighth as many people.

Finally, the financing plan is foggy. Laws would need to be changed to redirect the current excise tax set-asides for transit which, according to a 2006 attorney general’s opinion, can’t be used for "new public roads or highways." Uncertainty of a local funding source makes qualifying for federal dollars difficult, at best.

And, at best, what Cayetano offers in lieu of rail is a shell of a plan, unequal to the task before it: managing Oahu’s traffic demands. Voters owe it to themselves to call him on it before they head to the ballot box.