During the weeks-long debate over whether Metro should restore late-night service, one question remained unanswered: What exactly has the transit agency been doing with all the extra time it gained by closing early?

When the system moved to its schedule of 11:30 p.m. weekday closings in 2017, agency officials said the extra hours were needed to catch up on a backlog of neglected maintenance. Metro officials argued this year that they needed to maintain the early closings to support a new preventive maintenance program.

But D.C. officials, whose residents and businesses have been most affected by the change, have complained that Metro has never explained how the extra time has been used; what, if any, difference it has made in safety and reliability; and when the system’s old schedule might be restored.

“I find it very curious that there has been very little discussion, debate, questioning, probing about why Metro hasn’t been more efficient with the time and resources that it has,” D.C. Mayor Muriel E. Bowser (D) said at a news conference last week. “We have to demand that. We can’t have a system that has demanded more money and has gotten more money and has refused to work more efficiently.”

Bowser had pushed Metro to revert to its previous schedule of midnight weekday and 3 a.m. weekend closings or provide a firm date on when that would be possible.

“I think we have to get greater productivity on those off-hours,” said Metro board member Corbett A. Price, who represents D.C. and cast the lone dissenting vote Thursday for keeping the early closing. “It’s imperative for us to keep the system up and running with some reasonable hours.”

In the end, Bowser and the District lost.

Metro General Manager Paul J. Wiedefeld said the agency is in the process of conducting an analysis to provide a clearer timeline on its maintenance program to District officials. But his comments indicated that 3 a.m. closings would be a tough proposition in the near future.

“I definitely know that we can get back to midnight, for instance” Wiedefeld said. “I think that’s definitely within reach. I think we can do some things on the weekend. Whether to get to 3 o’clock, that’s difficult because that does squeeze out that window of work, and that’s where we were. That’s a little more difficult. But, again, let’s get the data to support it. That’s how we should drive it.”

Metro has argued that restoring 3 a.m. closings, would render the available work windows insufficient because of the time needed for setup and takedown of maintenance equipment.

Data obtained by James Pizzurro, a software engineer and lead developer of MetroHero, a free app for Metrorail commuters, supports the contention that Metro is working more efficiently during the extended overnight weekend windows. However, it does not necessarily point to a need to maintain 11:30 p.m. weeknight closings indefinitely.

The data showed that “shorter weekend hours were a boon for Metro track workers, while the extra half-hour of track time during the week has provided only a small benefit,” according to Greater Greater Washington, which first reported Pizzurro’s findings. “Metrorail track crews have been able to perform four times as much work on Saturdays and almost seven times as much work on Sundays through the first five months of Fiscal Year 2019 (July to November, 2018) as compared to the same time period before SafeTrack,” according to the data, the site said.

But the productivity increase was not so dramatic during the week, despite the additional half-hour maintenance window on weekdays.

“During the week (Mondays through Thursdays), little change has been seen in the cumulative amount work performed by Metro track crews,” the Greater Greater Washington report said, citing the data obtained from the agency.

Wiedefeld said Metro is turning to data to determine how long the agency will need the 41 weekly maintenance hours, among the most of any large transit system — up from 33 hours before SafeTrack.

The initial timeline for the preventive maintenance program has been set for five years. That process includes critical programs such as meggering — or insulation testing for the system’s signal cables — stray current testing aimed at preventing arcing incidents, for example, and efforts such as track bed cleaning and switch maintenance. Metro’s progress on those efforts ranges from a quarter of the way done to nearly finished, according to January briefing documents to the board.

But the two most labor-intensive processes, the cable meggering and stray current testing, are expected to take four and five years, respectively; Metro is 35 percent of the way through its meggering program and 23 percent finished with stray current testing, the agency said.

Metro sets what it calls “minimum wrench windows,” the amount of time needed to make the maintenance a worthwhile effort from a cost and efficiency standpoint. Meggering has a minimum two-hour window, while stray current requires at least 2.5 hours.

These figures provide an example, Metro argues, at why 3 a.m. weekend service, paired with 7 a.m. Saturday and Sunday openings, are not feasible.

One slide presented to the board noted: a “5 hour window is really 2 hours work window.”

Here’s the breakdown: Metro says the first hour of any system closure is spent fully clearing the tracks, or the time it takes for every train to move to its final destination. Next, a process lasting between a half-hour and an hour ensures the electrified third-rail is shut down and a work zone is safely established. Assuming the next two hours are spent productively, or as “wrench time,” the following hour is spent restoring power and moving trains safely into service, with a half-hour allotted to each.

The board voted 7 to 1 Thursday to give Metro what it wanted. It was a blow to D.C. officials who had spent two months advocating for late-night service to support restaurant, hospitality and service workers who need to commute overnight.

But perhaps even more frustrating to advocates and city officials, Metro has provided no assurances the same debate won’t happen again next year.

“We will patiently and determinedly move forward to get the late-night hours back,” Metro board chairman Jack Evans said. “Hopefully by next year we can get to midnight.”