For riders of San Francisco’s Muni light rail, delays have long been part of the rhythm of rush-hour commutes.

Trains and buses get stuck in the tangle of traffic. Debris gets caught in the tracks. Doors jam. Computers crash, and so do train control systems.

But now that the city’s transit board is tightening oversight on its beleaguered bus and light-rail system, Muni’s interim chief pledges to make noticeable improvements. In the next three months, acting transit director Julie Kirschbaum says she’ll cut stalls and interruptions by 10 percent in the subway and reduce the number of major stoppages — in which commuters are stranded for 20 minutes or longer — to four a month.

Kirschbaum took over for longtime transit boss John Haley, who abruptly retired last year amid accusations of bullying and harassment — another reason Muni came under a microscope.

It won’t be easy to transform a transit agency that’s hobbling along on old equipment, with trains navigating through tunnels that spill right into busy streets. The light rail that stitches San Francisco’s neighborhoods together is a complex orchestral arrangement, and when one small piece fails, it can throw everything off.

“In any major city, there’s always going to be issues,” said Joseph Laboy, a downtown resident who stopped by West Portal Station to shake hands with some of the workers Friday morning. He said they get a bad rap when anything goes wrong on the workhorse railway.

West Portal, a bustling hub with a top-floor bunker where Muni staff watches the paths of trains as dots inching along a switchboard, is one of the most complicated points in the system. It’s wedged between the Twin Peaks Tunnel and the intersection of West Portal Avenue and Ulloa Street, where the K, L, and M lines wait — sometimes for minutes — so cars, trucks and pedestrians can pass.

“If a car blocks that intersection, it backs up all the trains in the tunnel,” said Chris Donnelly, a Sunset District resident who has stoically tolerated the city’s transit mishaps for decades.

Kirschbaum put West Portal bottlenecks at the top of her priority list. Standing outside the station in a bright yellow safety vest, she pointed to various improvements the agency made during last year’s retrofit of the Twin Peaks Tunnel: a new, smoother track; new mechanical switches; a more sophisticated control panel that enables workers to pick which trains go through an intersection during backups. In recent weeks, she also assigned parking control officers to direct street traffic, a measure that cut delays by 40 percent this month.

Still, other parts of the system need help, too. Take the mechanical switch that broke at Church Street and Duboce Avenue this month, bringing the light-rail system to a slow crawl for 25 minutes at the peak of morning rush hour. The culprit? A loose bolt that prevented the switch from moving, which in turn stopped the control system from letting trains move forward.

Such seemingly small mechanical failures have dogged Muni for years. Since 2017, the agency has documented eight switch failures at Castro and Duboce, and four near the Embarcadero.

Last week, Kirschbaum told the San Francisco Municipal Transportation Agency board that Muni workers now install bolts differently, so it’s easier to tell when they are loose. The agency has also dispatched four staff members to monitor the Castro and Embarcadero switches.

Donnelly, the Sunset District resident, said he and other San Franciscans have grown accustomed to politicians and transportation officials promising to overhaul Muni Metro, followed by inevitable breakdowns. Over the years, Muni has become a colorful symbol of infrastructure woes, as well as a political football. Former Mayor Willie Brown made a 1995 campaign pledge to reform the system in 100 days — it sank three years later, during a well-publicized summer meltdown that led to delays of up to two hours.

In some ways, though, the current fix-it campaign feels different. Last year, the Municipal Transportation Agency’s Board of Directors requested monthly reports from Kirschbaum. These detailed analyses, coupled with regular 90-day improvement plans, have become a new way of doing business: approach each problem methodically, without any political bravado.

“I was encouraged by the seriousness with which Julie Kirschbaum took this,” said board Chairman Malcolm Heinicke, who initially pushed for the reports. He’s served on the board for 11 years and cannot recall the board asking for monthly presentations on bus and light-rail service.

“This is a different level of request from our board,” he said.

Heinicke will continue to press for better service at other points in the system, such as the two spurs that wrap behind Embarcadero, allowing trains to turn around. That process is so slow that it adds six minutes of dead time, often because drivers are chatting.

Kirschbaum said it may take a NASCAR mentality to make that part of Muni run more efficiently.

Correction: A previous version of this story misstated the location of a mechanical switch breakdown.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan