Metro’s newest rail lines were taken out of service Wednesday, so transit officials could begin immediate repairs of a “wire fatigue” problem that, if left untreated, could put bystanders in the path of a live electrical line.

“We think we can have this all resolved in a week,” said Tom Lambert, CEO of Metropolitan Transit Authority, though a permanent fix could take longer.

The emergency closing affects all of the Green and Purple lines, including the tracks they share downtown, along with the Red Line north of the University of Houston-Downtown station. All of those segments opened in the last six years, and were constructed together.

Lambert estimated 19,000 daily trips are affected by the shutdown, which covers 15.2 miles of rail. Buses will operate as shuttles, mimicking the rail route to provide service. Signs and employees will be positioned at stations to warn riders and direct them to the buses.

The work and shutdown will not affect service on most of the Red Line, from downtown to Fannin South. That portion of the Red Line carries about two-thirds of the agency’s light rail trips. Opened in 2004, the original line’s electrical system was designed differently and has not experienced the issue.

Metro officials shut the lines at 4 p.m. Wednesday, following two breaks in the wires in the past two months. The most recent, on May 2 at Dallas and Scott along Purple Line, occurred near a junction of two wires, as did another break along the Red Line just north of the overpass to the Burnett Transit Center on March 15.

“We do not have an answer just yet as to the cause,” Lambert said.

In both cases, the break happened where the wiring was slack, close to where the electrical system passes a post, essentially where the power jumps from one segment of wire to another. The breaks led Metro to assess what Lambert called “wire fatigue” at certain points along the line. In an abundance of caution — a break could lead to a wire falling to the ground, and electrocute someone, or catastrophically damage the system if the entire system slackened — Metro opted to close the lines and start work.

That left some riders frustrated for their afternoon commute.

“I guess I’ll just sleep less for a week,” said Sheryl Jackson-Baines, 33, who commutes to downtown on the Purple Line from her apartment near the University of Houston.

The plan is to attach wires before and after the junctions where the fatigue is happening, at each of 79 points along the tracks where the line passes one of the T-shaped posts that carry the electrical system above the rails. As crews attach the wires, the entire electrical system will be shut down along the lines.

Once the support wires are installed, Lambert said service will resume. The support wires will not stop breaks from occurring, but rather prevent the live lines from falling. It was chosen as a stopgap because it allow for safe operations, he said. Officials on Wednesday said they could not estimate how much the emergency repairs will cost.

Lambert and officials had fewer answers or expectations for a long-term solution. At this point, they are confident there is an “underlying cause,” operations Director Andrew Skabowski said, but they still are looking for it.

If the cause is found to be the result of poor construction or a defect of part of the design, Metro could seek damages from HRT, the firm that built all the new rail segments. The work remains under warranty for defects, said Roberto Trevino, Metro’s executive vice-president for planning, engineering and construction.

A bit of “wire fatigue” would not be the first hiccup with the new lines. Though construction on the northern extension of the Red Line stayed somewhat on schedule, opening in December 2013, development of the Green and Purple lines along Harrisburg and Scott, respectively, was slowed. Most of the two new lines opened in May 2015, though the last mile of the Green Line — delayed by a back-and-forth related to a freight rail overpass — did not open until January 2017.

During and since construction, Metro has contended with other problems or defects. Defective axle counters that were tripped by numerous things, including high water and candy wrappers, slowed train trips from the beginning until Metro and HRT found a solution and installed a new system in late 2016.

Not even the trains themselves were spared a painless entrance into service. CAF U.S.A., builder of 39 of Metro’s 76 railcars, was months behind schedule, something that reduced service even after the line’s first opened. Months into service, 14 of the cars had to be pulled suddenly because of a wheel malfunction.

dug.begley@chron.com