The debate over whether to complete Oahu rail to Ala Moana Center or stop at Middle Street needn’t be either/or.

The most rational course is to devote all existing funds to getting the train to Middle Street as soon as possible, using express buses to carry commuters to their final destinations.

Then, if public support and more funding materialize, a second phase of eastward construction can begin.

The reality is the city doesn’t have enough money to complete the full line; the half-percent rail excise tax and $1.5 billion federal share will raise $6.8 billion at most, while the Federal Transit Administration now projects it’ll cost up to $8.1 billion to reach Ala Moana.

The FTA also projects it’ll take two years longer than the city estimates, until 2024, to begin service to Ala Moana and says it’ll be flexible if the city changes course.

What better way for the city to regain trust than show it can competently build and operate a useful segment to Middle Street?

Holding out for Ala Moana or bust means another year or more of floundering while waiting to see if the extremely reluctant Legislature and City Council provide more funding.

Better to focus existing funds on getting to Middle Street and treat additional funding for building further as a separate issue that doesn’t distract from starting service to Middle Street in this decade.

This means committing no further rail funds beyond Middle Street until uncertainties are sorted out.

If existing money is spread out to include city center construction and new funding fails, we likely won’t even finish to Middle Street and will have nothing to show for nearly $7 billion spent.

The public is weary of such drama as rail costs have grown in a little over a year from $5.2 billion and promises of “on time and on budget” to nearly $3 billion over budget and five years behind the original schedule.

Facing reality and focusing on Middle Street for now would allow the city to map rail’s future without the pressure of immediately dealing with major utility relocations, business disruptions and other thorny challenges of building in the city center.

Future options could include finishing as planned to Ala Moana, switching to an alternate route to the University of Hawaii favored by many, or standing pat with the Middle Street rail terminus and buses if it’s well-accepted.

City officials worry stopping at Middle Street would sap ridership, but most municipal commuter systems combine rail and bus.

It works fine as an escape from gridlocked traffic when train and bus schedules are tightly coordinated, and express service and rush-hour contraflows are smartly deployed.

Those commuting to UH, Waikiki or other points east of Ala Moana would have to switch to buses either way.

Reach David Shapiro at volcanicash@gmail.com or blog.volcanicash.net.