Riders on four lines may notice their commute times grow in the coming months, as Metro slows trains to a maximum speed of 35 mph in critical stretches of the system, in what officials say is an effort to bolster reliability.

Metro said Monday it is imposing stricter speed limits on two track segments where trains were already limited to 45 mph, as officials aim to reduce power draw on portions of the Red, Orange, Blue and Silver lines. Trains have been ordered to slow to a maximum of 35 mph on stretches from Medical Center to Union Station on the Red Line, from Rosslyn to Minnesota Avenue on the Orange Line and from Rosslyn to Benning Road on the Blue and Silver lines.

Speed restrictions were originally imposed in those areas after the Federal Transit Administration issued a directive intended to reduce power draw last year, but the latest order — from Metro itself — slows train speeds even more.

Greater Greater Washington first reported on the new speed restrictions Monday, after obtaining an internal memo explaining the changes and that they could be in effect for a full year.

The restrictions come as Metro undergoes a power system analysis to address lingering concerns about the system that propels its trains, following a series of alarming safety incidents; a May 7, 2016, order to reduce power draw in high-risk track segments; and a December 2016 FTA report that noted a spike in traction power-related failures on Metro.

“The temporary order to lower the speed restriction from 45 mph to 35 mph is not a safety issue but a decision made to improve reliability until an analysis to optimize the breaker settings and power system can be completed,” Metro spokesman Richard L. Jordan said. “At that time, the temporary order will be adjusted as needed.”

Metro said the changes were expected to have a “minimal impact” on commutes because trains don’t travel at max speeds through downtown. The segments extend beyond downtown, however, and the 35 mph limit is far below Metro’s maximum of 59 mph in most of the system.

In an earlier email Monday, Jordan said the temporary order, which went into effect Sunday, formalizes slowdowns that were already in place — albeit less formally.

“Until now, this was communicated to train operators via radio. However, a temporary order has now been issued to the operating policy to eliminate the need for repetitive, standard announcements tying up radio traffic,” he said.

The slower speeds come nearly two months after Metro introduced new schedules lowering train frequency on five of six lines, amid ongoing budget woes. Under the new schedules, trains on every line arrive about every eight minutes at rush hour  — with more frequent service in the system’s core.