BART’s 20-year infrastructure repair plan is well ahead of schedule, officials with the transit agency said, with nearly 40 percent of planned work completed in only the project’s fifth year.

Voters approved the $3.5 billion bond measure in 2016 that allowed BART to replace aging rail and track components, some of which have been in use since BART opened 50 years ago, and modernize the system’s stations.

According to a report from the independent Measure RR Bond Oversight Committee that was delivered to the BART Board of Directors at its Aug. 25 meeting, BART had invested roughly $1.26 billion in infrastructure improvement projects as of March 2022.

Those projects — which include the replacement of 42 miles of rail and 46 miles of power cables — have led to a reduction of more than 500 service delays due to old and faulty track components since Measure RR work began.

BART Board President Rebecca Saltzman argued the reduction in delays has radically changed how BART can operate throughout the Bay Area.

“When I first got on the BART board in 2012, 2013, the number one complaint we got was about delays,” she said. “And there were delays all the time, and long delays, sometimes hour-long delays, and they were almost always because of our infrastructure that was failing.”

Some delays due to faulty equipment remain, however, like the failed power cable that caused a 16-day service interruption along the red line between Richmond and Millbrae.

BART officials said Measure RR work was accelerated over the last two years, as track workers were able to do more than their pre-COVID-19 pandemic capacity while the system’s hours and ridership were reduced.

In total, 38 percent of Measure RR projects have been completed. Of the 151 total projects that span from the planning stage to completion, an additional 50 are already in the construction phase.