Metro will pay a private company $89 million over the next five years to operate and maintain buses for nine bus lines in Northern Virginia, in an agreement that could pave the way for increased privatization at the transit agency.

According to the agreement, the French transportation company Transdev will be responsible for driving and repairing the buses that will be housed at the soon-to-be-opened Cinder Bed Road bus facility in Lorton.

Transdev will be responsible for about 5 percent of the bus service that Metro provides, with routes that primarily serve areas around Alexandria, Pentagon station, Franconia-Springfield station, Burke Centre and Fort Belvoir.

Though Metro has moved to privatize some of its more peripheral tasks, such as custodial services at some facilities or shuttle bus operations during temporary subway shutdowns, this would be the biggest-ever contract for privatizing day-to-day operations of the agency’s core services. Metro is estimating that the deal could save the transit agency $15 million over the next five years.

But officials with Amalgamated Transit Union Local 689, which has been in near-constant conflict with Metro management the last few months, are outraged. They called the decision to contract out operations at the new bus yard a “blatant attempt to attack the union members, lower worker morale and drive down the reliability of service.”

Union leaders say they are adding the bus proposal to their list of grievances with Metro filed with an arbitration board, pushing the argument that privatizing the day-to-day operations at the bus yard would violate their collective bargaining agreement.

The union had, in fact, submitted a bid to Metro to provide the services at the Cinder Bed Road facility, going head-to-head against four private companies for the job. Union representatives say their application was never taken seriously by Metro officials determined to continue the march toward privatization. Metro insists that Local 689’s bid was not considered because it was incomplete.

“The ATU submission was deemed nonresponsive because it failed to meet the . . . requirements in both form and substance,” Metro spokesman Dan Stessel said. “They did not respond with either a technical proposal or cost proposal and did not respond to any of the mandatory specified submission requirements.”

Consternation over the Cinder Bed Road contract is the latest point of conflict between Metro and the union as the two await an arbitration board’s decision on a new collective bargaining agreement. The previous labor contract expired two years ago.

The Transdev deal also could forecast what is to come as Metro considers privatizing some operations of phase II of the Silver Line extension when it opens in 2020. Metro, for example, could give a private company responsibility for operating the six new stations and performing track maintenance on the new stretch of the line, which will pick up at Wiehle-Reston East and continue past Dulles International Airport and into eastern Loudoun County, for a total of 23 miles of new track.

Matt Letourneau, chairman of the Metropolitan Washington Council of Governments board, called the Cinder Bed Road agreement “exactly what we’ve been looking for.” He said the decision to outsource some operations reinforces his confidence in Metro General Manager Paul J. Wiedefeld, and in Wiedefeld’s commitment to managing growing costs at the transit agency.

Letourneau recalled that just a few years ago, he suggested that Metro begin outsourcing some of its core services — particularly bus service — but the idea “was not getting a great reaction.”

“I think a lot of people told me, ‘Well, they can’t do that, it’s a hornet’s nest, this isn’t a fight we want to have,’” said Letourneau (R), who also is a member of the Loudoun County Board of Supervisors.

But as Metro deals with the possibility of having to make dramatic service cuts because of stagnant ridership and fare revenue, Letourneau said, there is a growing acknowledgment that keeping fares down is vital — for Metro, for riders, and for staff facing the possibility of future layoffs.

“I think people are starting to recognize that Metro is still facing an existential-type threat. This is a fundamental fight for its existence,” Letourneau said.

The Cinder Bed Road facility, which has been under construction since 2014, is slated to open at the end of the year. The facility can hold 160 buses, and the contractor will be expected to operate bus routes along nine lines that primarily serve Northern Virginia.

Metro estimates that the contract will bring 140 new jobs to the area.

Transdev, an international transit operations provider, also would be responsible for conducting basic repairs on the buses, maintaining the bus yard, and ensuring that all the routes and lines are properly staffed at any given time.

In a statement, Wiedefeld said privatization of the new facility will save the transit agency money in the long run. It also will help Metro keep a promise made to regional leaders to win support for a long-term funding package for infrastructure upgrades.

According to that agreement, Metro is legally required to cap growth in the annual amount that it can ask from each jurisdiction for year-to-year operating expenses. That amount can only increase by a maximum of 3 percent per year, unless the jurisdictions increase their scope of service (such as the operation of the new stretch of the Silver Line).

“Metro is working to contain cost growth,” Wiedefeld said. “This is a step toward keeping Metro affordable for riders, while helping to meet the legal mandate to hold subsidy growth for operating trains and buses.”

Metro also touted Transdev’s experience providing transit services around the region and abroad, hailing it as “the largest private provider of multiple modes of transportation in North America.” Transdev already has a business relationship with Metro; it’s one of three companies that provides vehicles and drivers for MetroAccess, which provides transportation for the elderly and people with disabilities. Transdev is not responsible for the dispatching of those vehicles, however.

And when it comes to privatizing bus systems, the region has had mixed success.

The District Department of Transportation’s Circulator buses, operated and maintained for years by the private company First Transit, have been plagued with defects and breakdowns. According to a 2015 audit, First Transit consistently fell short on maintenance duties, and the company’s failure to keep up with repairs and wear-and-tear had begun to take a toll on the useful life of the vehicles.

Those are the kind of problems that union officials say happen with privatization.

“This new contract will not save the system money without cutting essential corners of safety and reliability,” Local 689 said in a statement.

Privatization, the union added, is a “failed concept” that would allow “TransDev to set its own standards for safety, wages, and work rules, which will not be consistent with other Metro operators and maintenance.”

Letourneau said it is up to Metro to include the necessary contract requirements and inspection protocol to ensure that Transdev meets the transit agency’s standards. When transit outsourcing has failed in other places, he said, it has sometimes been because the locality or agency that outsourced the service failed to maintain the adequate oversight after the contract was signed.

“You can’t simply outsource and forget it,” Letourneau said. “It really just depends on the level of oversight you’re giving the contractor. You can’t just wipe your hands of it.”

Metro pointed out that the contract with Transdev for the Northern Virginia bus operations includes benchmarks the company must meet to satisfy its contract requirements. Those metrics include criteria such as on-time performance, preventive maintenance, cleanliness and quality of service for people with disabilities.

The contract “includes incentives for meeting or exceeding the metrics and consequences for falling short,” Metro said.

A spokeswoman for Metro said those consequences would be “financial credits” but did not specify how much money was at stake in these incentives or penalties.