In the wake of infrastructure-related service disruptions on the Washington Metropolitan Area Transit Authority’s Metrorail system—and a highly critical National Transportation Safety Board report on a fatal 2015 electrical-system incident—the agency plans to launch next month an intensive, system-wide rehabilitation program, aimed at restoring safety and reliability by mid 2017.

The proposal, which WMATA General Manager Paul Wiedefeld announced on May 6, seeks to carry out three years’ worth of work within one year on the 117-mile network in the District of Columbia, Maryland and Virginia. “This is a massive undertaking—no doubt about it,” he said.

Wiedefeld, Metro’s chief since Nov. 30, told reporters he had no cost estimate yet for what WMATA is calling its SafeTrack program but said it would not be in the billions of dollars. He said the task would require using outside contractors for at least some of the program, which would cover all aspects of Metrorail’s infrastructure. Some of the work will address priorities recently identified by Federal Transit Administration (FTA) inspectors.

The announcement came just three days after the NTSB pinpointed a prolonged short circuit in Metrorail’s third-rail power system as the probable cause for a January 2015 electrical arcing and smoke incident that killed one passenger and injured dozens more. A series of subsequent related incidents makes the electrical system a key focus of the rebuild, including third-rail cables, cover boards and boots, and replacing 12,000 insulators.

Another target is track, including rail work, replacing 36,000 fasteners and 48,000 wooden ties, and doing maintenance on interlockings. Tunnel lighting, ventilation and fan work are also on the to-do list.

Some of those tasks already have been fast-tracked. Wiedefeld said the system-wide replacement of electrical-system connector assemblies is expected to be completed this summer, a year ahead of schedule. There was no word on when WMATA might seek contracts for its new program. But if the agency’s board approves the draft plan, Wiedefeld wants to get started in early June.

The most drastic parts of Wiedefeld’s maintenance plan are temporary shutdowns, ranging from seven to 23 days, of five Metrorail segments. There also would be service reductions, using single-tracked trains, along other portions of the system. The longest single-tracking job—on the Orange Line in Virginia, between Vienna and West Falls Church—would extend for six weeks. According to Wiedefeld’s presentation, nearly all the shutdowns and service slowdown periods wouldn’t overlap with each other.

Wiedefeld said past maintenance practices had contributed to degrading the 40-year-old transit system, with an ever-lengthening list of repair needs outpacing the limited late-night and weekend hours available to address them.

In the 2015 incident, for example, NTSB investigators found that the arc tracking in a 16-ft-long jumper cable was aided by the presence of contaminants and moisture on third-rail cables and inside cable connector assemblies, which were found to have lacked required sealing components. Also contributing to the death and injuries were the tunnel’s 1970s-era smoke-detection and ventilation systems, which were designed for heat removal and temperature control, rather than for emergency smoke removal.

The safety board said WMATA’s organizational structure also compromises Metrorail’s safety. Its investigators criticized the absence of sufficient resources, technical capacity and enforcement authority of the rail agency’s safety oversight committee, composed of members from three jurisdictions. NTSB also said there were deficiencies at FTA, which was given temporary oversight of WMATA’s safety operations until a new independent commission is established next year.

In addition to providing 24 recommendations to WMATA to address system deficiencies, the NTSB called on FTA to enact regulations for tunnel infrastructure inspection, maintenance and repair that incorporate industry consensus standards.