Among the first things I do when I get to New York City for my annual visit is to buy a $19 weeklong pass for the subways. I love the N.Y. subways. And when I'm in D.C., I try to use the Metro as much as I can, but it's harder there. D.C. is like Honolulu; not that many people live or work within walking distance of the stations.

I'd love to see a train system on O'ahu if it made any sort of fiscal sense. So it's with regret that I know that when responsible and reasonable people consider the true costs of a rail system here, I'm confident that O'ahu will decide not build a train system.

Indeed, smart people ought to look past the politics now and save all of us the cost and angst of an effort that will come to naught. Why do I think this? Follow along.

Observe the light-rail system in Portland, Ore., touted as "a city worth emulating" in a recent Advertiser article. After 16 years in operation, it's attained a reported ridership of 97,000 trips per weekday.

Let's run some numbers using a very rosy scenario along with various estimates from Portland and Seattle. Assume a Honolulu system would somehow magically generate the same ridership as Portland in its first year, about 97,000 trips per weekday, equating to about 24 million rides a year. Assume each ride produces $3 in income, producing a total annual revenue of about $72 million. Assume that the day-to-day costs of operating the system are 80 percent of that revenue (the actual costs would exceed revenue, as is the case for most Mainland mass transit systems). That leaves $14.5 million for debt service. Assuming bonds paying 5 percent interest, that equates to a self-supporting long-term bond issue of about $250 million.

Put these computations in the context of Seattle, where transit proponents are trying to expand a monorail to a total of 10 miles in length (remember, it's a lot farther from Kapolei to downtown than 10 miles).

Estimates for this Seattle expansion — of an already existing one-mile system — range from $2.1 billion to $11 billion. If we assume that $5 billion is a reasonably accurate estimate for Seattle, an O'ahu system might run $10 billion, and $10 billion is 40 times more than a Portland-like system can support using its own revenues, even with the optimistic assumption that 25 percent-plus of O'ahu commuters would quickly abandon their cars and get on and stay on our new trains from opening day forward.

So where might the extra money come from on O'ahu? Maybe the feds will pay for some of the system — but they will not subsidize its operation. Let's optimistically assume that our clever U.S. senators can pull some pork our way and get the feds to pay for 75 percent of design and construction costs. We would still be stuck with coming up with $2.5 billion. A long-term $2.5 billion bond issue would add $125 million of new costs to Honolulu's budget every year. Honolulu's current operating budget is $1.85 billion, meaning that 7 percent more tax revenue would be needed to support our rail system. If we have to pay for half the capital costs, this means 15 percent more tax revenue will be needed.

It's important to remember I've used unrealistically optimistic assumptions that only a politician could propose with a straight face. Some will try to tell us that the system won't cost in the billions. They are either lying or they are dim-bulbs. And remember that it is likely that the system would run in the red from day one for many years, if not forever. Add those costs into the computations and a 25 to 30 percent increase in taxes on O'ahu is easily within the realm of possibility. Are you ready for that?

It's time to kill this project now — we don't need another $10 million study. Instead, Honolulu Mayor Mufi Hannemann can send me a check for 10 cents and we can be done with it.

Mike Rethman of Kane'ohe has been a Hawai'i resident since 1997. He was chairman of the Columbia (Maryland) Council in the mid-1990s. He wrote this commentary for The Advertiser.