WASHINGTON — Metro and the union representing its bus and train operators are in a court fight over work rules and overtime pay.

The transit agency filed a lawsuit in U.S. District Court on Friday, arguing that it must have an anti-fatigue policy which can block bus and train operators from working seven straight days.

Under Metro’s contract with Amalgamated Transit Union Local 689, senior operators have the right to choose to work seven straight days — the seventh day pays double-time.

Metro says that it’s concerned over the safety risk of potential fatigue, but to honor the labor contract, it has been paying some of these senior workers not to work, using next eligible employees, who are presumably more rested.

“It’s unfortunate Metro is trying to stand behind safety and say the union is against safety, in implementing their safety-fatigue policy,” said Esker Bilger, financial secretary-treasurer, Local 689.

“WMATA should honor our collective bargaining agreement, and we take safety very seriously,” Bilger said.

The transit agency is telling the court that, for safety’s sake, its anti-fatigue policy must take precedent over unionized workers’ choice to work a seventh straight day.