MARTA union employees held up signs and shouted chants in the shadow of a Midtown high-rise building Monday to protest stalled negotiations and privatization efforts that could threaten hundreds of jobs.

Contract negotiations between the union and the transit agency have dragged on for 16 months. The last contract expired in June, 2013. Amalgamated Transit Union Local 732 workers targeted the law office of MARTA Chairman Robbie Ashe for a midday rally in hopes of drawing attention to the impasse, said the ATU chapter’s president, Curtis Howard.

The contract comes up for renegotiation every three years.

Union workers have not had a raise since 2006. Meanwhile, health care costs and the cost of living have crept upward, said Rufus Silas, a College Park man who has driven a MARTA bus for 17 years.

“They’re slashing our benefits, attacking our pension, and now they want to outsource jobs,” said Silas, who was among about 100 employees who marched back and forth before the offices of Bondurant Mixson & Elmore at the corner of West Peachtree and 14th streets. “We’re sick and tired of being scapegoats.”

According to the latest available figures, MARTA has 4,553 full-time employees; 2,859 of them are represented by the union.

MARTA CEO Keith Parker is considering outsourcing some operations as a way to restore the transit agency to a solid financial footing. Those operations include paratransit service, cleaning, payroll and information technology.

The road map for such decisions is a 2012 audit by KPMG, a national consulting group. The audit said MARTA spent $50 million above the national average for employee benefits and could save between $60 million and $142 million over five years by outsourcing many functions.

But union officials question those projected savings. They say MARTA has yet to release the raw numbers used to calculate them. They also point out that a MARTA effort to outsource paratransit services failed in the 1990s due to poor management, and the transit agency had to retake control of paratransit.

The paratransit outsourcing alone could cost 300 jobs, said Jim Callaghan, who represents the ATU national office in Washington.

MARTA Board members were scheduled to vote last week on issuing a request for bids for paratransit service. However, the board tabled the discussion until November at the behest of union members.

Callaghan on Monday accused MARTA of deliberately stalling the negotiations in order to force the contract dispute into court.

A new law passed this year eliminated the old arbitration process, which union members felt was more favorable to them. Now, if the two sides declare a stalemate, a Superior Court judge in Fulton or DeKalb will resolve collective bargaining issues on a 90-day deadline.

A MARTA spokesman, Lyle Harris, said in an emailed statement that the union leadership has repeatedly missed or cancelled negotiation sessions since April, when MARTA put its last contract proposal on the table. Harris also said that, while union employees didn’t get a raise when the last contract was signed in 2010, they did get a $5 million lump sum payment. The payment was distributed by ATU to its members based on seniority.

“MARTA’s management has attempted to bargain in good faith since the very beginning of this process and will continue to do so,” said Harris.

The next meeting between representatives of the union and MARTA is scheduled for Wednesday.